tl;dr Endless and harder troll wave, so he should be in main focus, not killing every other enemy thing in wave.

Final wave on hard mode should be much harder, for now it looks like this. Kill many, easy and very tiny rogue/linebreaker spawns, then kill the troll. Also on the end, Troll's looping same behaviour -> walk some steps -> try to attack -> change player focus -> repeat. This is just boring and too easy.
This should be (imo) like this, that player's are forced to kill him, while being attacked by bigger and endless wave (maybe boolean var, so server could turn this off). There would be no easy way, just to take risk and try to kill him.