I apologize for barging in here, I hope I can say it a bit eloquently. But based on what you've said you have hardware-wise, I doubt an add-on would offer any improvement on your WoW experience. (Or removing an add-on). Of course it doesn't help you're running fairly large addons - it does add some to your load times, but your hardware is the issue. It's a bit on the low side; and I fear the only proper noticeable improvement for you would be an upgrade most likely.
What you could do, if you're unfamiliar with hardware is run this command in the Terminal.
Code:
sudo lshw -short >> hwinfo.txt
You can post the contents of that txt file here, it should be in your home directory. We might be able to help a little more directed.
