Dedicated GPU causes decrease in performance?

[Motherland]

I recently decided to try to do some offline performance testing with the beta, encouraged by the information that some optimization had been implemented and was surprised at my framerates which were pretty good (well, at least the game was playable). I then realized that I had neglected to force-on my dedicated GPU which is generally globally off on my laptop. I then went and checked and found that my GPU (NVIDIA NVS 5400M) has a similar effect on the current stable release, about halving my performance from ~80FPS to ~40FPS on mediumish settings (in Beta 6 my framerates drop from 35-40 under light load to about 12-15, meaning even using the hangar is difficult as the mouse lags)

I'm not concerned about having 'good' performance on my somewhat-old non-gaming laptop, just very confused about the situation, and I feel having a 20-30% performance increase that I imagine would come from switching off of integrated graphics, even to an underpowered mobile card, would put the game into 'very playable with cool graphics' territory.

The game definitely recognizes my card when it's activated, displaying it as the device in video settings and can see the extra video memory according to the GUI at the top of the ingame screen, so I'm really not sure what's going on. I just updated my drivers to no avail.

[Bizman]

They don't actually differ too much, 747 vs. 452 points in http://www.videocardbenchmark.net/mid_range_gpus.html. Both perform below the 9800 GTX (769) which has been mentioned to be somewhat of a minimum. Why the Intel performs better in the Beta might be due to shorter distances, better temperature handling or even solar flares. http://www.notebookcheck.net/NVIDIA-NVS-5400M.76731.0.html and http://www.notebookcheck.net/Intel-HD-Graphics-4000.69168.0.html show that the memory bus is similar at best, and both use the slow DDR3 for memory. However, the Intel uses 22 nm technology compared to the 40/28 of the Nvidia, which made me think about possible heat issues. Another thing that came into mind is that the game might trigger a resource hungry feature on with the "better" card, leaving that off with the other one.

Anyhow, when running at or below the bare minimums anything seems to be possible. 

[Skuzzy]

Disable all power management in that laptop, then try it again.  That is about all you can do.

Even then the 5400M is a very, very low end video card.  Not surprising it runs slower than the integrated Intel GPU.  Even uses on the Lenovo forums talk about how the integrated Intel CPU performs better than the NVidia GPU. 

[Motherland]

Well, that's surprising (to me at least). I was already running optimally (i.e. plugged in, power preferences full performance etc.)  so I guess that's just what I've got (this is an old, bogged down Windows install that I've been meaning to start over from though).
Thanks for the help!