High end PC - Weird frame rates in game.

First try updating any drivers for the 6870 and try again.

If that doesn't help with RIFT, overclock your 8120. Faster clocked CPU's in mmorpg's help A TON.

Drivers are fully up-to-date.

What should be a target clock rate? Also, I think, but my MOBO overclocks automatically?

Manually overclock, google for FX guides.

What cooler do you have?

If it's good, aim for at least 4ghz and try again.

Hyper 212 evo.

4ghz should be no problem for you.

welcome to the world of MMO's your gpu and your computer are fine. Graphically intensive areas of online gaming eg. Main cities have to draw each of the other people moving and jumping and other animations. This is so common and nothing to worry about. If you are struggling however overclock your gpu a tad.

Go for the CPU overclock.

I had a similar issue with WoW, processor Q9505, GPU 6870, playing in 1080p.

Overclocking the CPU from 2.8 to 3.2 GHz made a substantial difference; overclocking the 6870 to 1050 core / 1060 RAM only increased by a few frames a second.

Well, overclocking makes things almost worst. I manually overclocked to about 4ghz (which my mobo automatically does). I have had so many blue screens and random errors since I have overclocked.

This bugs the hell out of me. Is it because of the mother board? Should I go back to a 965? My old rig had a 955 and a 6850 and ran MUCH smoother and faster with NO errors or blue screens.... What should I upgrade or remove?

If you are encountering random errors and blue screens, I would think that you have pushed the overclock too far. Back it down! If this is an automatic overclock, turn it off.