For a class with effectively one useful damage skill (your choice of pos2+3 hitting skill) and absolutely zero utility, Black Mage really doesn't do *any* damage. He's got 22% less base damage than even the nearest vanilla hero, along with low base crit and lower base hp than anyone except the antiquarian. Even assuming you use Fira/Blizzara/Thundara and have 2 relevant targets to hit, you're still doing only at BEST comparable damage to other real damage-dealing heroes, and if you're forced to use Meteo to hit a single target, you're Literally Not Doing Any Damage (on top of the bad ACC bases for these attacks). And, we're just going to ignore the attacks that debuff your damage, since at any point where the damage debuff wouldn't be relevant to your ability to continue to project damage in a fight, the fight will already be at a point where the all-4 targeting of them will not gain full value (not to mention that with his awful base damage, the damage is mostly irrelevant in a burst sense anyways). At Black Mage's levels of glass hp and complete lack of secondary utility, he should probably be about in the 5-9 base damage range, but probably needs a general mechanical rework and rebalance to actually fit into a role without the overhead balance issues of the present targeting scheme of some of the skills (looking at you, repeatable all-enemy targeting and 3 redundant functionally identical skills).

Just my $0.02.