That's what she did in my game. All right, so it was more 'run up and shoot people at point blank range with her staff' than hitting them, but you get the idea.
I was going to suggest that you may have had her confused with Anders in DA2, because his AI was buggy and he often refused to heal the party... but I guess you are certain of this.
Anyway, are you sure your tactics were set up properly? Something like... Ally-Health < 75% - Heal ? If that's what you had, then I guess your game was bugged...
And moving on to something a bit more on-topic, I will just say that the Group Heal Focus power, whatever ranged Revival spell is at the end of the Spirit tree, Revival in general, health potions, regeneration potions, and grenades sound like more than enough healing options to me. Combined with the numerous ways of avoiding health damage, we should be fine... I really think Cameron Lee did the game a disservice with his sloppy play in that Twitch demo. He even said he wasn't really trying and that's why he did so poorly, but I think the fact that he was constantly low on health and then got wiped out is the only thing some people are focusing on... the game is not going to be that hard if we just pay attention and use our abilities wisely. He didn't and he said as much.