I like ESO, I really do.
It has great solo content, whether you just want to quest, gather materials, engage in thievery, or test your skills in Maelstrom Arena.
It has some fun and rewarding group dungeons for 4 people. I especially like thed the dungeons in HotR and am really looking forward to Dragon Bones.
It has challenging and rewarding end-game trials for 12 people. I'm not really a raid player, but they are clearly a huge draw for many people.
But - and this has been part of my feedback since
beta - there is almost nothing to do in PvE for 2 people, or any group without a fixed size. This quite often leads to situations where you can't play with your friends, either because you can't find anough people to fill the group for the specific content, or worse, you are excluded because the group's already full. Eventually this leads to cliques who often play together and it's
high school all over again.
It also means that the typical Elder Scrolls sandboxy feeling is very lacking in PvE content. Every noteworthy content is instanced, so you can't just go with any number of people and have an adventure somewhere.
Originally, ZOS seemed to be aware of this. Public Dungeons were especially designed for small groups, without a fixed group size in mind. They even have group challenges and whatnot. The problem is that a) there is no meaningful reward to be gained in these public dungeons, compared to group dungeons and b) like all overland content they are so incredibly easy that anyone can beat the group challenges on their own.
The original Imperial City Sewers solved both these problems. They had great rewards in Tel Var stones, key fragments and newly added VR 15/16 weapons, and they were much harder than any other overland content in the game (including free-roaming bosses, which we haven't seen anywhere else since). Since then, the difficulty has become trivial, and the rewards aren't that meaningful anymore - both problems that are shared with any older content in MMOs. The main issue, obviously, is that the sewers weren't strictly PvE content, but PvP.
Thus, what I'd like to see is
something like IC sewers for PvE only, or
veteran Public Dungeons around the difficulty of veteran DLC group dungeons.