So what kind of shutter speed are we talking?
Low ISO in extremely dark places, sounds like pictures where you have the time to setup a tripod or lean on something to take a picture.
Wouldn't you also have the time to take 7 pictures then? and make an HDR for some extra DR.....
Sure it is nice to have , but the 'need' for it may be overrated?
You chose to ignore the example I posted, how convenient.
No the "example" you posted is a perfect example of why actual photographers don't understand why some of you have such issues.
First, this scene does not have a wide dynamic range! There is very little DR in that scene, probably around five or six stops, a decent P&S can cover that range at 400iso.
Second, you didn't ETTR, you did use +0.33 EC but that wasn't enough for an optimal RAW exposure.
Third, your post processing exposes the fact that you just don't know what you are doing. Try this, I just did to your jpeg file. Exposure up 1.35 (that is where you should have been exposing by the way) Highlights down -37. That is how to post process your image, you have detail where you wanted it, but you have zero noise and banding even at 300% (with zero noise reduction).
Fourth, even at 100% and badly processed the banding is not serious enough to destroy the image, a little noise reduction and it is gone anyway, try +35 NR in Lightroom and it disappears.
Your "example" is not an example of failing Canon sensor capabilities, it is an example of you not knowing what you are doing at exposure time and in post. What you have illustrated is if you expose incorrectly, then process badly, then don't take any steps to mitigate those errors you can end up with slight noise and banding, you will forgive me for not taking your demonstration of Canon sensor issues seriously.
There is a kernel of truth in this DR "debate" but most of the "examples" posted just don't stand up and do not actually illustrate the "problem" at all, that is why there is such a staunch defense of Canon gear from some people here. You think your sensor failed you at that concert, it didn't, you didn't educate yourself on a competent way to use your equipment.