Yesterday I did such a good dungeon run with a tank, who only needed Regen to keep him alive... and the occasional Cure II if he got hit by a red. I was able to do so much Holy spam on the trash, because my bard friend was in the party with Mage's Ballad on after I got below 50% MP. The mobs went down pretty quickly. The tank was amazing, I'm surprised I never took aggro... once. The aggro meter never went above yellow. o-o

So anyway, if you have a good tank, Regen is definitely good enough to hold them up while you spam a couple Holy's. Also Divine Seal+Regen is OP xD