Hey man I have a 6 star kylo at max gear. He's pretty solid. The 5th upgrade for his outrage is 25% more damage when below 50% health. It's huge on his kit. He gets real tanky. His aoe starts to do decent damage(no where near 88 or maul). His auto attack is not great. But it does hit the heal block a lil more than half the time. And since he gets full counter after using his aoe it has a chance to proc on anyone using aoe. But really it's the outrage where his damage is at. When below 50%, poggles offense up buff is on him it will crit for a tiny bit over 11k. And that's a 1 shot for basically all the high damage characters. Since kylo is pretty tanky he can survive a round once he's below 50% health. Compared to other y star characters his power level is low. It's just a little over 3.9k where I have him. So it could bring it down if all your other guys are 6 and 7 star.
So in summary he's a hybrid character(health/damage). And his kit is legit. Counter,aoe, single target nuke. And I am slowly grinding him up to 7 stars as he has a place in my A team. He works well with sid or phasmas leadership. He's first order so he gets 32% chance to call ally assist under phasma. And the crit bonus from sid makes that outrage or any of his moves crit harder and a bit more often.
Hope this helps :)