Got my zealer level 88 in single players got a grief and use fanta.
If I were to slap that new bow with conc on a act 1 merc would it stack or would that kinda suck?

It will stack but you'll get more dps either with a might aura A2 merc w/ reapers/pride (but very hard to come by in single player) or an A5 frenzy merc with lawbringer and crescent moon

word, yea a reapers would be nice for physical immunes if i happen to get one