I have the exact same setup as you (do you have a HP Pavillion laptop by any chance as mine also comes with the switchable graphics)
What I did was the following as I was also getting seriiously laggy gameplay.
1. Memory limit increase - fix lagging (thz to TurkeyStyle).
Quote: - Go to C:\Users\[USERNAME]\Documents\My Games\Skyrim
- Open skyrim.ini, and check for [Papyrus] section. If it's not present, just create one at the end of the file.
- Add iMinMemoryPageSize=100000 and iMaxMemoryPageSize=5000000
- Add iMaxAllocatedMemoryBytes=1800000000
- WARNING! Do not increase iMaxAllocatedMemoryBytes value, because memory fragmentation may cause the game to crash or freeze.
2. Ensure that the 360 Controller is not enabled in game.
3. Activate triple-buffering (although I am not sure how this works as usually its for opengl games).
4. Alt-tab out the game and set the priority of TESV.exe to High or simply modify the .exe and add "-high".
5 If you are running switchable graphics make sure your card is set to use powerplay when using the high performance card (6770).6. Invest in a decent laptop cooling pad, a definite must if you want longevity with your current system, especially when playing graphically demanding games. I have always been a laptop gamer as I like the mobilty and this has been my saviour when I've seen many a friends system go down through overuse.7. Ensure you have the latest drivers from your manufacturer. You can't just log onto AMD and download the latest drivers with switchable graphics (not sure how it works with NVidia but HP has been pretty good in keeping the graphics drivers up to date on their website).I am now running on 1920 X 1080i using the ultra preset with AA at 8, AF at 16, FXAA ticked and it's playing beautifully
Please try the above and if you see any changes do let me know. I hope you sort it out. There is no reason your current specs should not be running this game on Ultra smoothly
Cheers
Stef