Hi
I play Lord of the Rings Online myself and the game does have times when it lags some but you might try showing the network connectivity icon in the game and see what your latency is running at when you see the lag.
To do this you go to Options, UI Settings, and activate "Show Connection Status in Alert Panel".
Your Latency should probably be in the 50 to 60 MS range normally, it it goes way up when you are lagging then this problem may be related to your connection.
Your computer certainly seems adequate for running these games, but you could try using DX 10 instead of DX 11.
You don't have to install a different version just tell the game to use DX 10.
You could set you page file manually, to about 1.5 times what your ram is.
http://kb2.adobe.com/cps/404/kb404939.html
You could install HWMonitor and see if the temperature on the components is getting high.
Link Removed
Run CCleaner
Link Removed - Invalid URL
If none of that helps then it might be some kind of hardware issue which takes it beyond my power to diagnose, but maybe someone else here could suggest something.
It's possible that it could be a ram issue, there are apps to test that.
MemTest: RAM reliability tester for Windows
I have had problems with my mouse acting up periodically for years and still haven't figured out why!
As a last resort you can run a repair install of Windows 7 and see if that cleans up the problem.
Repair Install - Windows 7 Forums
Mike