Right, I see your point, but you've got to waste 550 tp and 12 seconds on a fairly low powered skill in order to get a single infuriate usage out of it. Doing this multiple times in a fight would be pretty tough. If you DID do this, you'd have to wait for TP in between every fight slowing down progress and again, it'd not even work in most boss fights, changing nothing.

As for fracture, Berserk+Mame+Storms Eye+Unchained+Fracture crit Is one hell of a DoT, so I use it when I get that combo option available, but berserk is also situational, you don't want to be using it at the wrong time.