I mentioned this a couple pages back but didn't see a reply, I think the issue you are running into is because you are comparing hashrates from overclocked (stock or by the user) to your 'vanilla' 750Ti's. I have 3x EVGA 750Ti's and the rates I get from them non-OC'd are exactly what you are getting right now. However, raising the TDP and overclocking them to +142 core/+528 mem gets me the hashrates (sometimes a bit better) than what is generally quoted. Stock OC'd cards are in the range of  +100 core out of the box so that explains why some people with "stock cards" are getting better rates than you are.

If anyone is running a stock 750Ti with reference clocks and getting ~2.7MHs on X11 I'd love to see it