Almost every Merc healer I get while tanking is excellent at their job (except that one in Pyro spec with High Velocity Gas Cylinder on). They are also my favorite healer because they constantly shoot green stuff at me. PEWPEWPEW! PEWPEWPEW! PEWPEWPEW! Ha ha ha I ♥ them.
Anyway as far as my Healer class in Group Finder FPs, I usually see (hand-waving made-up rough guess pie chart here):
So, I have to disagree with you. Mercs, start queueing as healers! I'm tired of having silly bubbles around me every FP. I want more PEWPEWPEW.