If you are running minimum specs, which it loosk like you are, cant expect to run it on anything other than minimum specs. If you are trying to run it at a large resolution or turning on the eye candy, dont. Itll hamper performance.
Well, you passed the MINUMUM requirements indeed, but that's all the applet tests. I've always found those little things pretty useless, especially for MMOs where they almost always push the CPU more than the GPU.
You don't mention your exact CPU, resolution you play at, etc...
I played Rift for about 4-5 months on my old E8400 @ 3.6GHz, and it could get pretty bad in cities, PvP or during those insane invasions. I was gaming at 1920x1200 on a 4870 and the GPU was never maxed, the CPU however it was HELL (100% both cores)
I had to seriously gimp the graphics to have playable framerates (~35FPS in cities) on that setup.