Since we are discussing about mainly defensive buffs now, the simplest examples are granting a creature
+0|+X as a "pure" defensive buff, or
+Y|+X, where X should have a much higher vallue than Y for main defense with a small offensive component as suggested allready.
Those should definitely be in the poll, when we set it up, imo, since they are the most "basic" examples of a definsive buff.
When trying to turn my dive ability into a defensive one, i thought of doubling the HP and MaxHP of a creature until your next turn, thus halfing the damage done to it during the opponent's turn after returning to its initial state. I'm also suggesting this effect not to stack (probably showing an icon on the creature, that wears off after a turn), since it would be way easier to balance this way.
Edit: I'm disliking the idea of having a series of 12 swift-creatures, too, but having more than one shouldn't hurt.