Hello everyone!
In this thread I will go through (pretty much) all 'max stat' sets that are available in the game right now, list their conditions and my personal opinion for each. Warning in advance, it may be a more lengthy thread.
I will start with the most recent toning down, which was a good move;

The devs have given us their reasoning behind the nerf and it is;
Armor of the Trainee was meant as an introductory set that required no advanced strategy to utilize. The attributes it was providing were too high as you could get the same amount of Stamina that Draugr Hulk’s 5-piece provided, as well as significant Magicka and Health bonuses. This set will now provide less Stamina than the Draugr Hulk 5-piece, but more overall stats.
So what this basically means, is that since there is no 'condition' and you're getting a lot of stats overall, it needed to be toned down a bit. I agree with this nerf, the set was generally meant to be used by beginners and not end level PVPing. But you can still use it at end game if you wish to bump up all stats by a bit.
Now let's take a look at all other unconditional and conditional max stats sets;

This set looks nice but it's not popular because you can get more than what it gives by simply equipping 3 pieces of willpower (or ancient grace) + 2x of a monster set that adds max mag. However, I think that this is (approximately) how a max stats conditional set should look like on paper.

This set, compared to the previous one, overperforms a lot. Sorcerers can get the bonus from this set partially by using the atronach ultimate, or having either (or both) of their pets active at all times. From what I've seen, it also seems to proc off of anything that's counted as a pet (engine guardian?) and nightblades also benefit from it a lot (summon shade).
Compare this with the previous conditional one and there's no comparison. If you ask me, it should read exactly like the previous one and just have a pet as its condition, instead of a destruction staff.

This is a very strong set, I use it on my stamina templar along with hulking draugr and I am very happy with the performance. It's borderline OP when combined with hulking and a blue hp/stam regen buff, but the damage output is still reasonable since overall stamina isn't above 35-36k. As an example, you can build a mag sorc with 54k mag + 2k mag regen and enjoy a very strong shield, dps like a maniac and sustain pretty much forever. This won't let you do that but it will make you a lot tankier, which is its intended purpose.

As I said, this is a strong set as well, and I use it on my stamina templar without noticing much issues, but I've heard complaints from other players that it can overperform on certain stamina dk builds that push their stam pools astronomically high (haven't had the chance to get to it yet, but I definitely will). From what I understood, a redguard stam dk with this set is on a good track to becoming a sustainable DPS monster. I would still say it's great, but not as OP as necropotence on a high elf for example.

This one seems alrightish, I suspect most players that go for this would probably be either a magicka or a hybrid templar, focusing on blazing shield, possibly in a combination with a hp/mag regen buff to sustain their blazing shields. I do not use it, never have, so can't comment much on it, just listing it here along with others.

This is a good conditional set. It requires you to use a drink buff and fixes your sustain while giving you a bit of stamina as well. You can combine this with anything that says 'drink', even the witchmother buff that gives you mag/hp/mag regen, to get all 3 bonuses and both magicka/stamina regens to sustain utility and damage. There are other good buffs but most of them seem to be labeled as 'food' so this won't work unless your buff says 'drink'. Very good set.

This one is much better nowadays since you only lose 50% of your stones when you die, and getting 5000 telvars in an IC instance owned by your faction is fast. As its last bonus, this set will add you about 7k stats to each pool, and when combined with something like necropotence, you can pretty much play something like;

If you ask me, I'd change this set to give you a higher bonus towards acquiring telvar stones, or taking less damage from IC mobs/bosses, or both etc. but not semi-emperor stats with no sustain issues (for example, in this picture my stam regen is without major endurance and barely bumped up in the champion system, over 1000 will be easy to go for).
If I forgot anything, do include it. Let's discuss these sets a bit more, I predict that once proc sets are toned down and made not as interesting as they currently are, we will see a switch towards max stat sets, and some really crazy builds are a possibility with these.