I don't really use it when tanking, and I don't really plan to. Since it doesn't generate wrath, each use is one potential stack of wrath lost. Which means every five uses is a potential Inner Beast lost. Each fracture has 220 potency of damage in it, assuming you don't let it clip. Five fractures is 1100 points of damage potency. However, this is severely impaired thanks to Defiance, whereas 5 skills in your 1-2-3 combo and the accompanying Inner Beast results in 1280 potency ((150 * 2) + (200 * 2) + 280 + 300), 300 points of which is not impaired by Defiance's damage debuff. It also heals you, decreases incoming damage, and requires no TP to use.

So, while tanking, no, I pretty much never use Fracture. Maybe if I'm doing damage with defiance off, sure, but never while I'm tanking.