I have been testing different miners and different pools over the last couple days, as with the poster above I also saw a decrease of ~250 c/m with my GTX 780. I went from ~1730 to ~1400.
There is a different miner that gives me ~2100 c/m but it only runs on be^5r, so 'ill be looking around until I find a suitable one with either 1gh or ypool.