Video card driver
wise, I'd stick with that 10.9 that is working, you are no longer using a new gen card, and WoW being updated should not be a factor, at all.
I'm on a 5850 and using older driver too in PC I built in 8/2010.
Running fine for all games, including Rift.
Video card driver updates are usually because:
Known issue(s) fixed
New model is out and it needs supported.
If you are having no issues and/or driver developers notes don't indicate anything related to your
make and model, then it aint broke, no need to 'fix' (update) it.