I find it difficult talking about tanking on the forums sometimes, as the difficulty/skill level of tanking can be very different than something as measurable as DPS. If you are tanking end-game hard core content, but with a really good team - then frankly - tanking is fairly easy. Granted, you still want to have a solid setup and not mess up, but outside of that you won't get truly pushed to test the limits of the class. Same with more common place content like older and non-hardmode content (sometimes as we know you don't even need a real tank for some runs). The feedback I'm aiming for is more from experience with running with good groups, but not meta or BiS players and group compositions, where we actually are concerned with learning mechanics because we won't be able to burn through them, where you might be concerned with having a self heal on your bar as a dps, etc. When you are hearing that no one takes stam builds to vAS and they were all stacking magblades for the off heals, we were clearing vAS+2 with a stamblade and stamdk in the group and only one magblade providing off heals (just at a much slower rate of success lol).

The point is simply that I'm talking about doing the hardest content in the game without the most elite group of players on your team. As I've run a variety of content with various teams and guilds, I've noticed a big difference in what truly tests a class/build, so I'm giving my opinion based on these observations. As for what I've run, I have a tank of every class and I run hard mode end game vet dungeons and we are usually working on whatever the current HM-Vet trial is as well as mixing it up with whatever other trials we feel like doing week to week. I have the most experience on my DK, then my Warden and Templar tanks after that, I used to NB tank more than anything else the first couple years the game was out, but now I use that class about as often I use my sorc tank. Looking forward to necro tank, hopefully they offer skills similar to what I'm about to cover, but that doesn't mean we should ignore the existing classes either.

I will also not be using item sets to replace abilities. So pointing out Swarm Mother as an option for non DK/Warden classes is a non-starter as that makes the class weaker by taking away another monster set they could be using. (Though Silver Leash does help solve this issue now at least).

That said, I feel like there are a few key tools every tank should have (past taunting/blocking) - A solid Self-Heal, Self-protection, and some sort of group utility (and this is the area I think the different classes should have the most variety).

Self-Heals:

Good: DK, Sorc, Warden. Bad: Templar, Nightblade.

Here DK and Sorc have the best self heals. With Warden followed close behind, as their self heal isn't as strong, but they have several healing tools they can combine with it for a very responsive setup (that can even help the group on top of this). Nightblades and Templars follow it up (far in the back of this race) as a tie for worst. Nightblades were given a morph of cloak that offers a health-based self heal, but frankly it is horrible. I guess better than nothing, but it barely offers three ticks that hit harder than a good healers rapid regen ticks, combined with the fact that it's a HoT means it's not really useful to spam at all like you can with DK, Sorc or even Warden's (which has a stronger up front component than it's HoT). Templar has nothing to offer in the realm of health-based self heals, with really only breath of life as an ok option, which can go to anyone in your group in need of a heal, and has a high cost for very little return considering it scales poorly for a tank and won't hit that hard.

I think both Nightblades and Templars need some attention in this area for tanking. A morph of breath of life that scales off of health and is self-heal only would offer a good option as it would force anyone in PvP or even PvE to choose between a selfish version obviously built for tanking or a version that scales off magicka and offers more use to you as healer or DPS wanting to run an extra heal to help your group. As for Nightblades, they've already created a morph of cloak for this purpose (that I feel does the same thing for pvp where someone has to choose between the self heal or ability to go invisible) except that it's too weak to be useful in real end-game content (and the animation should be reworked as well). Maybe if they at least offered the first tick to hit twice as hard, then you could at least hit it a couple times in a row if you were in a desperate situation.

Self-Protection:

Good/Bad: I do feel like most of the classes offer a variety of protective abilities that leave them in good standing with each other outside of Nightblade.

DK has good self shields (that also offer a little shielding to group) and offer a heal buff when used, they also have spiked armor for armor increase and wings for reflecting ranged attacks and a couple of HoTs (which I feel fall more into protection than self healing as burst is usually needed when we look at those abilities). Templar actually feels very good in this area with their Circle giving them major buffs with bonus, a good shield that offers a protection buff for a short time and a (large in size) HoT that can offer some help to the group. Warden also does well here with Ice Armor providing a major armor buff not just for themselves, but for the group, protection buff for themselves when used, their shields are BiS for anything attack with a ranged attack, but do nothing for melee protection, and several options for small heal procs. Sorcs do have the major armor buffs with lightning form, but their ward is about as useful tanking wise as Templar's healing since it scales off of your magicka and not health. Fortunately their self healing options are fairly strong, but they do not have the variety of HoTs to put down as other classes. BUT, they do have an additional health bonus for running their clanfear self-heal that is a decent trade-off.

In this category I feel like Nightblade offers the least. You get a passive major armor buff when you use shadow abilities that does not seem like it lasts long enough compared to other classes. They have no shielding. Mirage feels useless now that evasion has been changed (AoE isn't something that most tanks really are concerned about). And their HoTs are fairly weak for a tank to run as path doesn't hit that hard in a tank build, but their self heal hits well enough that I guess we could call it a decent short HoT because it definitely isn't good enough to fall into the self heals above. I feel like Mirage could be reworked to be a more useful option for a tank here. Leave one morph as it is for a DPS or PvPer to use that actually want evasion, but offer one morph aimed more for tanking. I'm sure a variety of options could be thought up to make it different than what other classes already have, we could have a regenerating shield on top of the minor armor buffs it offers - something like giving 3K shield a second, if you don't get hit it stays 3K (it doesn't grow or anything) but if you take damage, then the next second it regens to 3K again - similar to how Lunar Bastion set works but for self only.

Utility:

DK offers small shields for their group, some small off-heals, and one of the most useful buffs in the game right now: engulfing flames.
In addition to that, they also have great crowd control with Chains and Talons. And they have the best "oh crap" utlimate in the game with Magma Shell.

Warden offers great buffing and healing for the group, even with tank stats. The only class that offers Minor Toughness. Has some a great mob control using portals and can snare with Ice, though no hard group CCs. They have a couple decent Ultimates: Trees with a decent heal for cheap cost and Sleet Storm for Major Protection.

Templars offer an armor debuff no other class has with minor pen, even though this is often run by a healer, it's worth mentioning as a positive I think and could free up a bar slot in a 4-man run. They can put down a large area HoT that offers a purify, they could run heals for others though they will not be strong as they scale from magicka. They have no real CCs (I suppose the morph of javelin could be an option). For mob control they are forced to rely on Silver Leesh and could run Bombard from Bow if needed - all very stamina intensive. Their healing utli isn't great for tanking, but Nova does at least offer protection if needed for a particular strat.

Sorcs have a great CC with Encase, even better than Talons for some situations. They have to rely on Silver Leash pull mobs. They don't really offer any group HoTs or other utility. Though I should mention from a selfish standpoint that Bolt Escape is a great and unique tanking tool for some situations. Negate is the best option they have class wise as a defensive ulti and Storm Atro can be a good buff/tool esp for a smaller group.

Nightblade has a ranged major armor debuff with Mark Target if needed, not really a go-to always use utility, but worth mentioning. Mainly because outside of that, they don't have a lot. No CCs, no pulls -- well, one CC - fear, but it does the opposite of what you usually look for in a tanking CC. Path offers a HoT but is pretty weak in a tank build. Shadows to offer Maim, so it's nice to have that tool coming from a magicka cost if needed, but they don't really have any stand out tools that make anyone happy you brought a NB tank. Consuming Darkness is their go-to defensive ultimate, which isn't bad especially with a decent duration.

What does all this mean for utility rankings?

Well, in the end, engulfing flames is the most useful single ability outside of just crowd control. Unless you are in a 4 man with your two DPS running stam builds, it's hard to pass up. And in a trial where you will often have several mag DPS using fire if not all, it's impossible to pass up. Personally, I think this is the one instance I would nerf instead of buff. I think engulfing should be a self buff only - increasing the damage of the fire damage of whatever DK cast it and would turn into a tool to use for a DK DPS to self buff. The only other option would be to treat this in a manner for every class to offer some kind of damage buff that does the same thing. Maybe Sorc Tanks could use an ability like a morph of mage's wrath to apply a lightning damage bonus for everyone in the group, or Wardens an Ice damage bonus (lol I know) -- the difficult thing with this would be the power creep of pretty much offering every class bonuses because DPS would be able to apply them as well. So I think the nerf to engulfing would be best for the game. Even if everything was equal on all classes, this skill would still make DK the go-to and as it stands, they aren't equal and their are a dozen other reasons that DK will still be go-to for BiS tank class.

I think Sorcs and Nightblades need the most attention in this area and Templars a little as well. Bringing a DK? Great - shields, talons, chains, eng. flames. Bringing a Warden? Great - toughness, ice armor, heals, portals. Those are the only two classes players are usually excited to see show up because they know they will be adding something to the run. Past that it's usually just whether or not you can get the base job done when you show up on other classes.

Nightblades used to offer something interesting with Sap Tank builds using Sap and Siphoning, but these have been nerfed to the point where they aren't really that great anymore for tanking and one of the skills isn't even used anymore for any build really outside of niche use. Could possibly rework sap to do more, if you don't want to let it regen as much as it used to, it could offer more group buffs, regen buffs, or even a short one or two second heavy snare, (like 70%) when you hit something with sap, that way if you were hitting it over and over again it could act almost as a talons/encase CC to keep mobs together, but wouldn't just be another hard CC like those and would create a constant cost that would make it hard to use that way for PvP. The healing morph of path could scale somehow based on your highest stat or average of all your three stats, so even if a stam or tank build ran it, it would still offer a decent heal.

Sorcs could have a morph of mage's wrath that wasn't an execute, but made a target more vulnerable to off balance - and I don't mean a better proc chance, but take away from the immunity cool down for a boss, allowing someone keeping this skill up to double the off balance uptime on a boss fight. This would also be something that a DPS would probably not run, as they would either leave it off their bar completely, or run the execute morph of wrath.

There are some out of class skills that are useful for tanking and help even things out: Silver Leash was a great change - it's not as good as having magicka abilities IMO that do the same thing, but if you have to have a pull for certain runs then it's a great option to have. Barrier is a decent defensive ulti and of course War Horn is the go-to tanking ulti for group runs. Time Stop is "ok" for a CC, the timing and now higher cost make it not a great option much of the time, but at least it's something.

In Summary:

DK is still the de-facto tanking king IMO. With Warden coming up right behind them offering some benefits that DK can't. This is how tanking balance between classes should be handled: Offer a couple of the same basic tools: self heal, self-protection and then offer some different utility skills that give each class something different to bring to the table.

Nightblades and Templars both need some attention in the self-heal area, even though some changes have been made the last couple years to make them better at tanking, they still have a ways to go.

And both NB and Templars plus Sorcs need some attention in the utility area.

Even then DK will still have the most to offer IMO, but if you narrow it down to wanting to run a given class to preference and not just need it will go a long way. Part of the reason tanking is boring lately isn't just the fight design, but also the lack of options for end-game tanking. Lack of class options and lack of gear options.