There is probably a good reason for ignoring the APS-C lens market. At my previous job, everybody who had a non point and shoot, had a Rebel XTi, with the OLD 18-55 non-IS kit lens, and was happy. I couldn't convince any of them to even try the 50mm f/1.8. The boss had apparently considered trying the lens a few times, but never did.

I suspect the majority of Rebel buyers don't buy lenses. The camera kit itself was a large enough expense that they're not willing to invest more. Even the 50mm f/1.8 is out of budget. It's not economical to produce fast lenses for the few APS-C users who do buy lenses. The people who are shooting fast lenses are either trying to lower DOF, or lower noise with lower ISOs. That super narrow subset of APS-C shooters aren't a viable market, and this non-viable market can easily put themselves into a viable fullframe market that will give them the thin DOF and low noise they desire at a variety of price points. From $500 used 5DmkI, $1200 used 1DsmkII for servo, $1900 6D, $2700 5DmkIII for servo, or $6000ish 1DX for all the latest bells and whistles.

Because of servo performance needs, a limited budget, I recently went with a used 1Ds2. I *really* like the quality I get, even with an ancient fullframe body. I can't see myself going back to a crop body. I don't shoot enough wildlife to justify lowering the quality of the rest of my photos. My 7D mainly gathers dust along with the T1i. If I *knew* the 6D could handle my servo needs, I'd sell all three bodies and pick up a 6D.

DxOMark show the 5DmkI outperforms your T3, and the semi-pro 7D in image quality and ISO. If you're looking for fast primes, you're looking for the advantages of fullframe. Why not get one? For the price of a lens, you can have everything you want*, just not in lens form.

(* = Assuming you weren't just hoping for something lighter!)