The bugs are pretty annoying really
Followers not using abilities
Followers including the the Inquisitor and enemies just freeze in place
Varric using an ability that I haven't even picked
I'm tot sure if enemy mages are bugged or just really overpowered because its close to impossible to dps their barriers down. One dispeller isn't even enough. Had to bring 3 dispellers just to actually kill them. Even worse when there's two
Ran into the followers not using abilities when I started tresspasser. Closing the game and relaunching it fixed it, and I didn't see it again. Annoying, but fixable by relaunch.
Characters freezing in place affects the whole game, and is, I think, the most annoying bug, as it makes you have to keep an eye on everybody every battle, just so that if they freeze, you can switch to them and make them jump, which breaks the freeze.
I didn't have Varric with me, so didn't run into that one. Didn't notice anyone else using abilities I hadn't picked.
The mages are tough with very high barriers - but that wasn't a major annoyance for me, just made some battles more challenging.
What annoys me is the level 27 hard cap - you can't progress higher than that, and I'd reached level 27, with the DLCs, WAY before trespasser. It totally takes away from the game when your chars can't progress. The level cap should be removed, and a "soft cap" be allowed to be the only barrier, like it was supposed to be.