I triple box healers (plus 2 dps) for our raids. Resto Druid, Holy Paladin, and Holy Priest. What I usually do is assign a tank to the druid and a tank to the paladin and then raid heal with my priest as my main.
Congratulations on the raiding success. It's a ton of fun. And I hear ya about the repair bills. If there is one thing I've learned with boxing raids, it's that when things go wrong, they really go wrong! But that's what dailies are for!