I’m not sure what you mean by “chugging” and I honestly haven’t played offline before, but I think it’s a common issue.
My system is upper mid-range and runs the game very well, but every now and then it hits a “snag” and freezes for about half a second. Generally doesn’t happen very often but it’s noticable. I’ve seen a few posts about it on the community site so I think most people have this happening.
A related problem (for me, I’m not sure if everyone gets this one) is that I’ve had it freeze on me a couple of times before on that snag. Judging by the sounds, the game is still running and my controls still respond, but the screen image is frozen on the frame that it snagged on, forcing me to ctrl-alt-delete out. Pretty rare but quite annoying if it does happen.