The main reason for the low performance is the almost insane amount of objects used for Nehrims immersion.
The world is filled up with so much cluttert, etc. that the engine is at it's limit.
And sadly that's a point, where SureAI can't do anything.
Try some mesh-fixes, ini-tweaks, a.s.o.
http://sites.google.com/site/ballofflam ... nceproject
^
It a good start into that topic.
Don't forget to optimize your system with stuff like defragmentation, registry-cleaning, etc.
(Tools like TuneUp Utilities, CC Cleaner, etc. will do the cleaning, things like Auslogics Defrag will keep your HDD smooth)
It wouldn't hurt to shut down some background programs either, f.e. firewall, antivirius, etc. if you play offline)
Also, please not: FPS arround 25~30 are just fine.
There is no use in higher FPS, since your eyes/brain won't notice any difference.