I don't see much of a difference with ccminer. I am still getting 6.8./6.9 Mhash.
Here is my config: nvminer.exe -d 0,1 -a dmd-gr -o stratum+tcp://dmdpool.digsys.bg:3333 -u user -p pass
Any additional flag that you are using to get 7.8? Or perhaps are you overclocking the card?
I'm in my car right now. When i get home I'll lookup what I used to test hash with. I know it wasn't the same pool you used.
I also used stock clock speeds but the 750ti is a higher end Gigabyte OCed card.
I will post clock speeds also.