What exactly is bad about using the environment in a battle? You still can (and should) use your profession-specific skills (I used blink, torch-stealth, etc. constantly). I still feel like a Mesmer.
In my opinion new mechanics make encounters feel more special and varied. The boss gains much more of uniqueness if there are things to accomplish which other bosses don't have. You just have to learn new mechanics (I know, not everyone can do this easily) and master them to beat the boss. Imho the best videogame bosses are programmed that way.
The one thing I don't like about the update are the boring boss-models of Glint's Lair. We have seen that enemy-model too often already, why did they just add a bigger version of that model as a boss? Why not something entirely new? I love the new Mordrem btw.