I think it'll be tame if you change the effect to work on successful basic attack. So not on AoO, and for the love of Batman not on full-round attack. Post-10, that bit won't matter, but it boosts your drain before that.

Also, consider: after 10, deals damage equal to pool but still drains half of it. That will make it more dependable as an attack while balancing the defence bit, if it turns out too strong.

As for Paths, an idea is the heavy-armored/shielded that is particularly pissed when attacked, and a more reckless heavy-hitter (give him free Monkey Grip if you're feeling evil).