The problem is that unless the support buff is enough to change a benefic into a malefic (and with a cohealer and our host of oGCDs is that really likely?) then the DPS cards will always be preferable.
What I feel would be better is if you get a second 'play' action after the card, which would be a support/healing effect.
Though Bole's issue is still here - you can't ever guarantee that you have the right support skill. If you can't plan for having it, you have to assume that you won't have it.
