I've never noticed my attack or defense power go down after he uses it. I've been wondering for years what it's supposed to do--I just call it the "Phew, I get to live for another turn" attack. I think Culex uses it too.
Maybe it is something like removing the effects of potions. I tend not to use the potions, so I wouldn't notice.
Hee hee. Shredder. That new TMNT series on CN is absolutely awful.