Recently, I've started to play World of Warcraft again . During fights like Ultraxion in raid finder, my fps dipped to about 20 FPS. In Orgrimmar on the Arthas (mid pop) server, I get about 20 fps. Is there any setting or any sort of things I need to be doing to increase my FPS? This is a mild (at best) improvement over the last (vastly inferior) setup I had. I just can't fathom a world where I can run Battlefield 3 better than World of Warcraft.
I can run battlefield 3 at high/ultra settings @ 1920x1080 at about 45-50 fps. I'm trying to play wow at 1920x1080 with relatively similar settings.
This is normal, they are extremely CPU intense fights, to help you can disable data collection addons like recount and disable your combat log, view distance and removing AA for certain fights may help.
On Ultraxion 25 HC everyone gets bad fps, I get about 20% GPU load in wow, it's all CPU man. Overclocking your CPU will definitely help also.
Outdated addons. That is the most likely your problem. Since you mentioned you started playing again, you probably didn't update them? Try turning them all off and see if it's better. If it is, download new ones.
Also, did you OC your CPU?
I've got 2500k @ 4.3 GHz and 560 Ti. On highest settings, on Ultraxion I get between 50-60 fps WHILE frapsing, and I get around 40-50 in Orgrimmar at peak hours.