As a "roleplayer" - it's a little gross to want to play a "healer" instead of using things like Barrier. "No, I want you to bleed so I can HEAL you!" That's such a twisted thought process.
Prevention will always be better than reaction even if most people aren't smart enough to do it well.
That's unfair. No matter how good one is at mitigation or healing, some wounds are going to take place. It's a realistic goal, as an extra challenge for a player, to try and play in such a way that no party member is ever incapacitated. It's not a realistic goal to aim to prevent any party member from ever losing health, even if mitigation completely replaces healing. A game in which this was achievable, even if it was only achievable through great skill, would be much too easy. So, given that some wounds will always happen, a person isn't twisted for wanting to be able to get rid of that hurt. This is especially the case given that we're talking about an already-established universe in which magical healing is possible. If we were going to design a new setting from the top down, and someone contributing to its design said: "I prefer healing over mitigation, because I want people to get hurt so that I can heal them," then that would be twisted. But that's not the situation here at all.
It's also not a fair representation of the known abilities as they stand. Previously, mages had a number of healing spells and one damage-prevention ability. (Maybe more if we see buffs like Rock Armour as damage prevention, but I don't know if that's in DA:I, so I can't compare. As such, I'll leave buffs out of the equation.) Now, it seems that mages have one damage-prevention ability, albeit one that can be evolved and developed to have extra effects as the game goes on, plus a single heal that can be used very rarely. That just seems like having fewer options, but hopefully I'm wrong.
Anyway, I could do without your comment that "most people aren't smart enough to do it well." Every play style has advantages and drawbacks that can be used cleverly by a tactical mind.