Trying to run this on a laptop?
Sounds like your CPU is topping out at 100%. Had a similar problem with my PC.
Run the windows task manager before you start the game, then start the game and alt-tab out to the task manager and select the performance tab. If your game was like mine and running on one core only, you'll see one core topped out at 100% and the other barely used.
So fix that issue through windows (if you're using win7, you won't have this problem), or the control panel in Nvidia.
Another performance boost for slower CPU's is to right-click the divinity2.exe in the task manager and select the priority level to high, you'll get a warning message, just ignore it. Alt-tab back to the game and resume play.
HTH
