[ASK] Are healers supposed to stop healing troops?

So, today I attacked about twenty times, always with same army and a dragon in my clan castle. I always had one healer in, that one healed the giants I planted it right next to, all going well...until the giants died. The healer did pretty much nothing then, it neither healed my archers which were 5 fields next to it nor did it heal my dragon, 3 fields next to it.
Is this supposed to work that way, or is healers' behaviour just bad implemented?