The activated ability on this creature feels like a concession that the controlling player can't dependably profit off of the static ability, rather than an added function that improves the design. It also may be too strong of an effect on a rather large common, though I haven't personally reviewed the common forms of removal in the set. Personally, I'd prefer a more universal (and simple) static effect of "Creatures that have been dealt damage this turn can't block.", which I suppose might have to be templated as a triggered ability.

I don't know what it was before, but the simpler version seems interesting to me, and appropriate flavour. Mainly useful with ping effects, since they can prevent a big creature from blocking without using themselves up, whereas wasting a burn spell on something it can't kill will rarely be right. But in that niche, it's quite nice.

­Pyroclasm and suchlike makes him unblockable for a turn, which is quite good. Except by things with prot-red!