Your rig is running it just fine. Don't be alarmed by the temps - as people have said, this game is optimized very poorly. Your lag could be from a handful of things. I know people hate the questions buuuut...

1. Torrents?
2. Anti-virus?
3. Multiple programs? (Steam is actually a huge memory hog, for example)

Also, someone else pointed out that there is server lag since 1.22. I myself haven't noticed it but it can happen. Also...

1. What times does this occur? Some IP companies throttle down bandwidth at peak hours.
2. I am assuming you have a LAN connection but, is it possible you are wireless?
3. Do you have multiple people connecting via the router at the same time (PS3 online, another PC downloading, Netflix on a TV, etc.)?

Sorry, I am just looking for non-hardware bottlenecks first.