What level does he have? And gear overall.
I picked a3pnb hell on my light trap sin to test this(had a5 previously). He's using wizspike with ms diamond, griff -18, +7 teeth armor -16, hhg -8, craft boots +1 30fcr triple res, arach, souldrainers, ele gaze set. Impressions: well he seems like a good companion for a solo gameplay/psn chars. He kills what I can't - Light immune harlots - rather quick 3-4 shots(1fireball a3fire merc) only because they don't go near him/shadow master tanks. When I tried to leave him alone vs a single minion of destruction, well, he failed and died. I joined few pub wsk runs 4-5ppl and well, he can't kill anything on that spawn. Maybe that's because he loves to spam that psn attack/bone armor instead of teeth/spear, or maybe magic res is too high. Overall he's not bad a merc but nowhere near useful in parties(well no need merc in good parties
) and he's stupid(no nec would cast teeth, switch to bone armor, poison cloud, bone armor again, bone spirit and 2nd teeth), so far fire/light are my favorite (never had a blizz on this season, just know they own stuff)
Feel free not to change anything on him, or just adjust nm bonespirit to match hell, looks more like a typo