Rage spell. If it stops stacking with that, it's a big loss.
Basically if that's the case, it's a huge nerf to dedicated melee DPSers, who have few spellcasting abilities (just clickies). It's arguably a buff to those that use UMD regularly. A big buff to melee arcanes/divines, and even casting arcanes/divines, if they're not using DC-based stuff.
Which, you know, is exactly what the game needs right now... those DPS Barbs and Fighters are just steamrolling far too much content.