Great body/lens pairs

I have some excellent images on my wall at 20x30 that came from the T4i. I am happy with its abi.ities and aware of its limitations. Fortunately for me (or, as a result of my careful research) the camera's limitations are in areas that generally do not matter to me. For example, I've never shot 6fps bursts and never filled the buffer.

That said, the basis for my point about the camera (sensor) being a limiting factor was looking at DxOMark ratings for lenses with different bodies. Take, for example:

Sigma 50mm f1.4 DG HSM A

Sigma 50mm f1.4 EX DG HSM

Canon 50mm f1.8 IS II

On a T5i/700d, the Art has a sharpness of 15 P-Mpix, the regular Sigma 11 and the Canon 12. On a 5DS R, those numbers rise to 40, 19 and 21, respectively. Thus, the Art has a lot more to give a high-end body, but maybe not such a significant difference on a 700d. (Unfortunately, there are no tested with the short-lived T4i/650d, so this is the closest comparison.) Looking at the total score, which includes other factors such as distortion and aberration, there is a similar substantial difference between bodies: 44, 35, 34 respectively on the 5DS R and 24, 20, 18 on the 700d.

Thus, we are back to the original point: sure the Art improves on the lowly Canon on a 700d, but it really shines on a better body. Is it really worth 10x the price when attached to a 700d (or in my case, a T4i)? In my case, I think not.

I'm looking for others thoughts on what they have found to be good lens choices that get you most of the way toward the image quality of a far more expensive lens. The 80/20 rule, if you will. And maybe throw in a little discussion about other attributes that were nice improvements over a lesser lens.