Almost every one has said you are not supposed to tank everything, and its true, but there is aggro generation in this game. It just works a bit differently than other games. Here are some tips from memory that may help you. Some of this is directly from a devs article or interview or some such, the rest I have read in a few threads on how tanking works in this game.

Proximity! Mobs are more likely to attack people close to them, being the closest person to a mob generates aggro on that mob.

Who hit them last. In this game it is not so much damage itself but rather the attacks that generate aggro. So for dps, lots of fast but light hits will pull aggro from the tank quicker than slow Heavy attacks, even if the DPS of the hvy attacks is higher.

Damn when I started typing this I had more but now I realize the details are all a little fuzzy and I really don't want to spread miss-information. There was a thread on here about how to tank effectively in this game but it might have been a beta thread that got deleted.

There is however a very large and quite informative thread on tanking on Tamriel Foundry anyone that wants to tank well should probably read if a search here doesn't turn up anything.
tamrielfoundry.com/topic/tank-theorycrafting-thread/
*edited since I should at least try to add a link to said thread*.

So much cooperation.

I really do love the way tanking and healing work in this game. I'm not holding onto everything, but I am able to taunt multiple mobs in a row and keep them away from my group.

I do spend some time running around compared to other games, but it helps me keep an eye on my party. When I see someone getting hurt , I drag whatever is on me over and pull another mob off a party member.

Since I am a healer sometimes, and a tank others... I have come to appreciate tanking, aggro, and stamina/magicka management. Mobility is a requirement in nearly every aspect of the game... and things just feel more active.

More enjoyable.

I would really like to LOL at most of the comment here... only because things don't work in the same way as other game doesn't mean that they don't work at all...

Tanking lots of mob impossible? WRONG ... it can be done
No aggro generating abilities? WRONG there are abilities that generate more aggro than other... simply tooltip don't tell you all you need to know... and this is one of the major problem of this game... that is to say a huge lack of information... (well someone find it amusing... for me it is a minor annoiance since I usually test things for myslef and don't base my judgement on tooltip and second hand information...)

let me elborate...

what generate aggro in this game? this is the first question everyone that want to tank should ask himself... but people go with what is standard and toally skeep this... let me tell you that DAMAGE is not the main source of aggro... instead what generate LOT of aggro is IMPOSING CONDITIONS and also it seem to generate aggro at the moment the condition is applied (this apply for dot as well all the treat they produce is generated at the moment of application and not distribuited trough the dot duration... so reappling the same dot over and over seem to generate quite the large amount of treat) also the simple act of HITTING a target already generate an ammount of aggro, the amount of damage dealt increase this value but except for nukes usualy multi hit generate more aggor than strong but single hit, this transalet in "pulsing" skill or channeled skill to be good aggro generator and there is quite a few of "Pulsing" aoe skill (ash clous is an example if we talk of DK... or even inferno...).
Last CC and how they relate to aggo, when a player get CCed he loose all aggro... this mean that if a tank get hit by a CC skill than all his effeort in building aggro is lost... and this means that you must KNOW what to block and should never allow yourself to be CCed (blocking an attack that have a CC among his effect will not only halve the damage but will also TOTALY NEGATE the CC component)...
At the same time CC also have an additional effect on mob as well, incapacitating CC (stun, fear, disorient and the like) reset the aggro table of the mob... so as a DPS using an aoe Stun and than stay close to the group of mob will not be a really wise choice since they will agrro the closest enemy first as soon as they get out of the CC and all the previous treat built by the tank will have beeen long gone...)... using CC can be at the same time a strong tool or a horrible pass for a quick wipe... use it to reset aggro when the tank is loosing it... youe them as opening when the aggro is still not decided, use them when all the dps and healer can get out of the mob reange... but never do it when the tank is holding the enemies.. and over all never use AoE CC when you ongly have problem with a single enemy... you will end up screwing the aggro of all the mob in the area ^^'


for aoe tanking just apply those simple knowledge... for DK this traslate into a few MUST HAVE abilities...
1) Burning talons (root + fire damage + chance to apply burning... lot of aoe condition in one go)
2) ash cloud (snare, 30% miss chance and pulsing damage every second... again conditions and multihitting)
3) firey breath and relative morphs (aoe fire dot + chance to apply burning... aoe condition FTW if you havent understood it yet ^^' )

defensive skill are not as essential as in other game since you already have a BIG damage mitigation ability... that is BLOCK ... let me tell you this again you must know WHAT TO BLOCK if you want to tank... with a good understanding of blocking and just one defensive ability you already covered most of your survival necessity as a tank... what is left is "specific cisrcumstance that require specific skills" ... such as for example damage shields that are usualy not necessary for a tank (useful but not a necessity...) but that can turn some SPECIFIC fight from hard to easy... or gap closer that normaly you don't really need (for trash you can simply walk on them there is no need for charge and that way you also avoid the delay between the charge animation and the animation of your first AoE effect) but can be really effective in fight that require lot of mobility...

hope this help...

These was an official post on grouping and roles by the dev team:
elderscrollsonline.com/en/news/post/2013/07/01/inside-eso-dungeons

I'll highlight the Tanking bullet points here:

• You won’t need to get every enemy’s attention. Every player can take a few hits from standard attacks, and they have lots of ways to take care of themselves. Many healing abilities affect an area, so your healer (if you only have one) should be able to take care of several party members.
• In a fight with a large group of enemies, a tank’s ability to control the fight is critical. Stun the healers, interrupt the spellcasters—you’re the best party member for the job, because your stuns and interrupts will tend to get those enemies to attack you back.
• You do need to stay engaged with tougher monsters, like bosses. They hit much harder, and your damage mitigation and extra health will keep you alive where other characters might die.

Yes I have noticed that some abilities tend to generate more agro than others specially the ones that apply conditions such as CCs or DoT. Its a pity tooltip or any in game tutorials don't talk about agro generation in this game.

But still i'ld like to see some authentic and clear post from the devs confirming exactly how agro works in this game. The instructions they have supplied by now in various posts are too scattered and vague at best.