More leftovers from Monday's Avacyn Restored spoiler extravaganza:
What a terrible card. Sure it's a 3/4 flier for 3 mana, but... this can't be good in or out of limited, can it? For limited, it isn't big enough to deal enough damage to end the game within 1 or 2 turns (like Ravenous Demon). And for constructed, there are just much better options.
If you really wanted to play the taskmaster, I suppose you could try to force it into a mono-black aggro type deck that featured Gravecrawler or Bloodghast, but I think you would just find yourself playing a terrible mono-black aggro deck. Do yourself a favor and pass on the taskmaster. (And he's not even a zombie, which doesn't help his case for existing.)