Ok, more updates:

When I try to launch the script from above, with value set as 0,0,1280,500 for x y w and h, the application does open up, but I get an AppleScript Error saying "World of Warcraft got an error: Can't set bounds of window 1 to {0, 0, 1280, 500} And the window is exactly the same size as normal.

Now, when I open up one of my WoW config.wtf files, I see the line about 6 or 8 down saying SET gxResolution "12800x800". If i change the numbers here to 1280x400 or 700x800, when I launch the program my screen is indeed closer to the right size, but it's not exactly right, and is often very stretched or squished, depending on which was I split it.

So any other ideas? Man, I wish something like maximizer worked on macs :S I'm surprised no other mac users are splitting their screens for this.