Also added on to what blackmogrim was saying... leveling a spriest so far seems to have no issues with mana that it used. Granted I am not terribly far at this point... leveling the whole way as shadow looks like it might not be awful anymore.
I sure as hell hope they change something about the clunkiness of the apparitions themselves. I mean, since they become an actual resource using ability having them wander aimlessly because they can't reach their target or because the target died is a very big loss in their potential damage output. This was never as much the case with how Apparitions work now but I feel the mobility needs a workaround to say the least.
I did a Ragefire chasm dungeon today (which they have totally changed) and one of the bosses is now a worm thingy like magmaw and he goes down into the lava to move around. My apparitions were going through the platform to hit him while he was down, which is pretty cool.