I've never though about this until it just popped into my head, if you were to use his ability on multiples or turnabouts, since it is dealing X damage, it's printed, would this work if my opponent blocked, or if it was reduced? I know normally it's a no since it is not considered to deal damage when it doesnt deal damage (dug) but here X is actually 0, so am I just hoping for too much here, or does this actually work?

The AGR Says:

8.3.3.10 An attack must cause a vitality loss of at least 1 or more to your opponent to be considered to have dealt damage.