Yeah what Valence says. It's just too fast with too much visual mess. I find it really difficult to pick off boss tells and remembering cast names is also challenging (possibly because once I've cleared a MSQ dungeon I don't touch it again). I did switch from MCH to WAR to get through the MSQ dungeons with NPCs, but I still found it difficult and frankly unpleasant.
To loop back to the issue of rotations, struggling players like me are told to not worry about doing damage, first avoid the mechanics. Very sensible, but also a massive indictment of fight design. And the less skilled you are, the more the fight reduces to DDR. Why learn what your kit does when you don't have time to use it?
The other huge issue I have is button bloat. If I wanted to use all my kit, I can't because I simply can't create that many comfortable keybinds.
I figure in terms of skill, in PvP I am top 20%, in PvE bottom 20%. A huge chunk of that is that in PvP I don't need to look at either my hotbars or keyboard. And I enjoy PvP.