Why Kill Spell Power?

Blizzard is simplifying stats in Cataclysm. Which I welcome. Stats are so complex at this point in WoW that I actually need a mod to tell me if gear that drops in an instance is an upgrade over my current gear.

But as always, there's a bit of a wrinkle.

For casters, there are a number of rather complicated statistics. There's spell penetration, which I have never really understood at all (although I believe it gives extra chance to hit if your target has resistances, which no player or mob does anymore). Haste, Crit, and Hit are pretty easy to understand -- they make your spells cast faster, crit more often, and hit more often, respectively. Except they are a little weird because you get "points" of these three. So you don't get 2% faster casting, you get like 47 points of haste which is completely meaningless unless you know the conversion for points to percentage haste (it changes with level).

Then there's spellpower, which is probably the easiest to understand of all. One point of spellpower gives you one extra point of damage for a 3 (or 2.5?) second cast spell. So a 3 second spell always gets one extra point of damage for each point of spellpower.

So guess what stat Blizzard ditching in Cataclysm? Spellpower, of course. Guess what is being kept? Haste, crit, hit, and spell penetration.