Do you understand the damage lost from entering Defiance?

Making up the hp difference from entering it cost an additional cd, you are now stuck in it for 10s doing ~30% less damage.
-5% for leaving Deliverance.
-25% for being in Defiance.
Reduced Crit rate and the inability to use Fell Cleave over IB which is a 200 potency difference.
If you Unchain instead of IB, what are you mitigating?

It costs a lot to be that tanky, it most certainly is not the best of both worlds, it's one or the other.