Here's one to consider... Having an extra healer when you're learning a fight is like riding a bike with stabalisers. You don't need it, but you go longer without falling off!Our main problem was the lack of dps the whole night. 7H is too much anywhere. If you can't make it with 6 (whatever the fight) then you are doing something wrong - either the healers, either some failed mechanic.
My point being, what worked out well last night was that we could tinker and tune the raid with immunity to some of the mistakes that take us out early. The side effect of that extra healing was the attempts lasting longer and I guess people getting used to the 'No BattleRez' approach. When we switched out Pol to DPS we were well oiled and the kill came on the 2nd try with that setup.
I suppose there will always be an argument that we might have made it 2nd try from the start if we'd been a DPS up from then?
Another view though, our healers are prolific signers. I'm quite happy to take the extra heal while working on the fight and mechanics and then look at off spec for a DPS if needed. It worked that way as that was the signups we had.
Blizzard has said that in this raid mechanics rule, wipes should be mechanic fails more than DPS checks. If extra heals absolves the odd mechanic mistake we can live with that.
Final thought. It helped that Poli pulled exceptional DPS. I hope it lifted the bar for some of our DPS.