I don't know who you have and haven't done for the boss fight meme, so which of your characters would have the most mechanically complex boss fights?
Complex!!! Alright, I've already listed one really complex one which was Vuisce, how aboutttttttt..........Drieg! Never talk much about em!
Drieg is extremely deceptive, in that their fight would seem like a cinch from afar. A daredevil sylvari? So problems here just stay long range and try to outpace them right?
Drieg isn't just your standard sylvari though, they've got a trick up their sleeve. Literally. Their skin is toxic, and tiny hairs are constantly flaking off. Throughout the fight the air will get thicker and thicker with AOE poison damage. The more you hit them, the more hairs you knock loose and the worse the air gets for you. The closer you are to them, the worse it gets as well. Every 10% of their health that you take out though, you'll get a shot at their CC bar for a momentary window. If you manage to stun them you can move the fighting ring! They will follow you outside of the range of the bad air and it gives you a chance to reset on those conditions.
If you fail the CC bar, the fight will not move and the conditions will keep stacking. If you miss the CC bar twice, you'll start getting sporadic blindness as well due to how saturated the air is with tiny toxic hairs.
At 50% health Drieg will increase in speed as well and focus more on keeping close to you than purely damaging you with their staff, to increase the condition damage to the player.
If you get them down to 5% health, you will win and they will retreat, promising to come after you another day. Sleep with one eye open, stranger.