I am likewise experiencing the same issue, and Blizzard's response so far is extremely aggravating.
08/28/2012 05:54 PMRebooting your computer is always good. It can solve many problems.
Posted by S4d1k
It's comments like this that make me the angriest.
When you see a major performance regression from pre-patch to post-patch and the basics have been tried (clean out cache, disable addons, reset SMC, etc), then that is most certainly not normal, and should not be portrayed as such. This is a bug. I don't mind it not being fixed yet, but I do want to see it acknowledged for what it is.
It is very rare (even in a game like WoW) for a graphics intensive program to hit the CPU so hard. Seeing 100% CPU on the login screen (when the CPU should be doing next to nothing - not even on the network or loading addons yet) means you have single-threaded code running in a tight loop - probably busy waiting, polling, or a similar routine is running amok.
Any developer will tell you when you see a program hit 100% of CPU almost exactly on a multicore system, that means single-threaded code is running as fast as it possibly can. Multithreaded code would consume all cores and look like 200%, 400%, etc, depending on how many cores you have. Sometimes you want all cores used - video transcoding for instance, which is extremely CPU intensive. Sitting at a login screen and seeing the same behavior is a bug, and the CPU usage has nothing to do with graphics, frame rate, etc.
I'm running a 2010 MacBook Pro with dedicated graphics, 8GB memory, SSD, on Mac OS X 10.8.1. I'm seeing the same thing in both 32-bit and 64-bit modes. I've likewise performed all of the recommended troubleshooting steps, and no change. Observing this on two computers (I also have a Mac Mini 2011 with integrated graphics), and also on the MoP beta. Yesterday my CPU usage was negligible; today it's 100% on the login screen and 180% in game. Limiting FPS does not change this (because FPS rarely has anything to do with the CPU - that's all GPU bound).
We now have dozens of reports across desktops, laptops, Lion, Mountain Lion, 32-bit, 64-bit, 5.0.4, MoP beta - in a nutshell, it's a Mac client specific issue, and it's not tied to a specific hardware, graphics, or local setting/account configuration. It doesn't get much more clear cut.
Until this is fixed, WoW is a complete non-starter for me - it's frying my computer.