Bruh, ability to kill one enemy with stripped armors for 4AP isn´t "making any difficulty a joke". For 4AP, your ranger or rogue could kill that guy anyway and probably deal some aoe damage in the process...
I play with a modded chicken that only lasts one turn, so rupture doesn't kill an enemy. But it does up to 1200 damage for 2 AP when my ranger hits for around 230 with an autoattack. For 4 AP you get a 1 turn cc + 800-1200 damage. Even if i could do that damage with my ranger with 4AP, the chicken combo has still a cc in it.
What level are you at for enemies to have so much health yet still deal poor damage?
IF you're around 13, you should be having legendary crossbow and deal up to 2k per turn already and whne you get to 16, 15k per turn. Yes, 15k. Arrow storm is broken.
I'm level 14 with a level 13 epic bow. I just use what i find. And if arrow storm is as you discribed it, my group would have surely outruled or nerved it. One broken ability doesn't make another any less broken.
So yes, there are many broken combos/abilities, and all of them make the game incredible easy. For a propper difficulty all of them have to be reworked.
And if a level 14 boss has 800 shield +2000 health, dealing 2k damage per turn on a single character is totaly broken. So i really cant understand how you are defending the balance of the game.