So, it's become a regular affair in my playthroughs that occasionally the game will just clam up and drop to single-digit fps--functional enough for me to quick-save and quit, but way too laggy to play (like 5-10 seconds of latency on click). I figure it's just an issue with Vulcan that will eventually be worked out.
More importantly, I've been noticing that these graphical fits are frequently triggered by firebolts and fire-terrain effects appearing on screen. Now, I understand graphical issues are complicated and it could very well be a phenomenon unique to my machine, but if others experience this same issue, have you noticed particular events that trigger it? It might make for useful data.