I wouldn't make a rule of just PoH/CoHing once per, just do what is needed while keeping the renews refreshed with direct heals.
Binding Heal is wickedly awesome in this situation. It and Renew top my meter breakdown on this fight. Don't stop using PoM/CoH/PoH, chakra states are not a binary spell selection.
And don't be afraid of being too liberal with Fheal. The rolling renew amps up the hpm of Fheal. Between that and the mana pool reset black blood provides, have fun with it. It's a very easy fight to heal once you get the rhythm down.