I run three healers in random bgs. Priest, druid, paladin. They only have 1500 r esilience. Im unkillable without a zerg but i cant do any damage. Unfortunately im alliance so i probably lose 80% of the battles. Im usually the top three healers though.

Running 3 toons doesnt seem to cause any problems in the 10 man bgs.

In wsg i try to follow the flag carrier. If they outrun me or run into a zerg on purpose i just heal people in mid after that.