Teleport ranged units within arm's reach of anyone with an attack of opportunity, especially if they can trigger status effects on hit. Archers don't much mind but mages seem to like to try to run a step or two away. Alternately, featherfall someone over to them if you prefer.
If you're abusing the oil puddles, just generally turn everything everywhere into a nightmare of fire and brimstone. Be sure to line 'em up and Bull Rush someone across the lake of fire, so your opponents lay around like slabs of ribs.
Create a giant puddle, wade your melee into the middle, freeze everything, then hit your own melee with minor fire damage to unstick them. Sure, you do less damage to frozen units, but you can pretend to savor their crystalline tears as they get chipped to pieces.
Stealth (or better yet, Invisible) around behind some enemy units and open the fight with a Bull Rush. Get everyone situated while the AI staggers around trying to stand up. Hilarity ensues, of whatever flavor you find most delectable.
Three (or even four!) mage team; each character with enough DEX to equip a halfway decent bow. 'Nuff said.
