With the new changes :

/castsequence reset=whatever Power Word:Shield, Heal,Heal

is more than enough to keep my tank at full, at least in heroics...

This is a very mana efficient rotation, also helps with the overhealing(%90 of my healings were overheal before the patch)...

With it; Penance became like a low-cost, quick emergency spell for me, in case i need extra healing on tank or on slaves taking heavy damage. Therefore it is not in my rotations for the priest as i like it to be not on cooldown when i need it.

Of course this is more related to individiual playstyle... I always had a tendency or reflex of trying to cast Penance when in situations above before the patch only to get frustrated to see it on cooldown as it was on my tank rotation. So taking Penance out of the rotation made me happy and suited my playstyle, but it may not for someone else.