I almost never comm the other healer, mostly because I typically do 80% or more of the healing. On the rare occasion that I get another healer that heals, they get the comm. Otherwise it goes to the tank if they main tanked and didn't mess up badly or if they actually picked up adds. In the rest of the cases (that is, the majority of the time) I give it to the dps that aggravated me the least.
