Only if the single healer is a priest really, which is why only PMR is viable for them to solo, since the MR can pretty much survive by themselves for quite long.
Well, I think the combo we play is actually pretty good against them. We try and put alot of early pressure on them, even though we have 2 healers, I think the key for us is spam dispelling the warrior, trinket early to keep pressure up, then combine their first Ice Block with BOP/PS, which should force the priest to spam heal the mage, leaving the priest to burn mage or priest (not sure yet what's better).
We need more games though, only did 2 games vs PMR since I fixed my setup to be able to dispell faster <_<