Here's the problem with ESO right now when it comes to DPS: PVE players use less than 10 sets total. It's all about a handful of trial sets and an even smaller handful of non-trial sets, and the only non-trial set that is actually good outside Arcanist and Templar, is Pillars of Nirn. I'm not saying having a non-trial set be good is a bad thing. I'm saying having so few options is a bad thing. There used to be a larger number of sets available for us to use that were kinda good, but even back then, sets like New Moon Acolyte, or even older, sets like War Maidens, though they were considered good, they weren't meta.
Over the years, the meta for both PVE and PVP has shrunk into a couple sets. If you look at any meta PVE build, you'll probably find some combination of four sets:
Pillars of Nirn, Arms of Relequen, Whorl of the Depths, and Coral Riptide
...or Deadly when it comes to Arcanist or Templar.
4 (kinda 5) sets to rule them all, and only one is a non-trial set. But of course, you should pair a trial set with a non-trial set, since otherwise you won't get that 5% bonus damage in PVE, but having it be so limiting... There's literally hundreds of sets in this game, over 75 of them are crafted. I mean, just look at the release of Arcanist, 11 whole new sets! But how many are meta? None.
My proposition is this. Buff all DPS-centric sets in the game, and make them all comparable.
Every set should be good for different reasons. There should be a bench mark of around 120k dps for two sets + other things like a mythic, monster helm set, and/or ability altering weapon. With practice, knowing your rotations, picking the right sets that work well together, that should be the benchmark, with your class coming into play on top of it all.
You should be able to take any 2 damage sets in the game and make a good build out of it.
Make it so if you don't do a trial set you generally deal ~5% less damage due to that passive, that's fine! Make some sets only work for certain classes, like how Deadly is pretty meta for Arcanist and Templar! But players should have a million and one choices when it comes to damage dealing, not just 4. Make it so we can grab like... Unfathomable Darkness + Spell Strategist and, along with your other choices of gear, you can hit those high DPS numbers.
This goes the same for PVP sets. Set a benchmark, and make it so that's the benchmark to meet when it comes to the power scaling of the sets for that content. Same with tanking sets and healing sets and support sets, all of these are important. We have so many choices, but none of them are good? This should not be the case.
Obviously there are some class problems right now as well that I wish were addressed. But this thread is focused on the set problem.