It seems that the performance of the game has improved since my last cleanup and re-tweak. Emptying the WDB and WTF folders seems to have helped somewhat with the low frame-rates that I was having a few days ago.
Another thing I noticed that improved performance was decreasing the screen resolution from 1650×1050 to (goes to check the resolution, it’s at 1650…so never-mind!)
I thought the resolution had something to do with the performance of the game, but apparently not. It seems to be working okay for now. It’s still laggy and slow in Dalaran, but it’s to be expected.