I don't see the mix. It works but it seems clunky and slow. I know AOEing is going out with wotlk, but DS is pretty worthless on single targets, maybe they should put it back on mana and let you decide to kill your mana pool or not.
They are putting it back on mana and it'll share a cooldown with Crusader Strike but it's intentionally worthless on single targets. It is an AOE after all.