Last week my 10-man team lacked Replenishment. On our first heroic BQL attempt my mana got low, even with a mana potion and casting Plea and Trinkets on cool down. We had three healers, a restoration Druid, a discipline Priest, and Big Healer(me). Being a Holy Light spammer, I was tossing out big heals on the raid liberally on anyone that didn't have a full health bar. This attempt failed when a Pact'ed pair didn't close in fast enough.
Attempt #2. My plan is to only use Holy Light when another healer has Pact or Swarming and during the Air phase. I would Aura Mastery Shadow during the first Air phase, pop wings and blow out heals to everyone. The second Air Phase would get Aura Mastery and Divine Sacrifice and of course Holy Light spam.
This plan requires that I trust the other healers in my team to be healing too. On most fights, I don't run out of mana, so I don't really worry about over healing and it all goes to the tank via Beacon anyway. My Flash of Light heals range from 7k to 10k, which is between 1/4 and 1/3 of a typical raiders health. I have 2 other healers backing me up so that should be enough. Of course if anyone looks like they are going down fast, a big heal will be coming.
This plan worked great, the raid stayed up, vampires all hit their marks, and the Queen died just as she was going into the second air phase (maybe Divine Sac during 1st air phase next time). I was spamming my 1 second Flash like a Hyper healing machine. My effective heals were lower then on the first attempt but people didn't die and I was never too low on mana to cast a big heal. Trying to top the meters and playing smart are not the same thing.