I previously blogged about the abundance of specialized statistics in WoW. One thing I lost track of while juggling all of the various ratings and powers and attributes was how stats don't actually mean the same thing for different classes anymore.
For example, all five of the game's attributes can, for some class/spec out there, add spell or healing power to your character sheet. If you're a Retribution Paladin, one additional point of strength gets boosted by 15% through talents, another 10% if you have Blessing of Kings up, doubled to turn into Attack Power, and you then get 30% of the final number back in the form of spell power.
Would the game be better off if it had only two stats (attack and defense)? In some ways the answer is no - it's nice to be able to dictate that you're doing to focus your offense on critical hits to take advantage of certain talents. I'm sure it also helps Blizzard fill out the loot tables when they can offer side grades within the same tier of items. The problem is that then you end up with a mess where it's very hard to figure out how to weigh the various ratings.
I don't think this got noticed as much with the transition from level 60 to level 70, as the jump in gear quality was so great that either you were replacing everything, or you had been raiding for long enough that you got to put off gear decisions for a few levels. The jump from Outland to Northrend seems a bit smaller, though, so this change is going to hit a lot more people a lot earlier than it did last time out. And good luck if you have alts who cover all the different class roles - so many formulae to memorize, so little time.