I don't really agree that the fight wasn't tough enough. It MIGHT not have been. It might well have been perfectly fine too. There's no absolute rule of thumb about it. I'm just saying that party A and party B may expend different amounts of HS in fight, all else being equal. In that case chances are the party coming out ahead in HS was more optimal for that particular encounter. Heal heavy parties are likely to expend more HS, thus likely to be less optimal in a bigger range of encounters.
Sure any party is likely to not use every power it has in most encounters. That's not really the point. They have the OPTION to use those powers or not and if those options are better options then they're better off.