I did sell my 24mm PC-E last fall after being frustrated with it's soft corners in comparison to the 14-24. Especially since there's no DxO profile for it, being a shift lens.
BUT, this is for professional architectural work, shot at f8-f11, needing maximum sharpness, and often being printed at 36" or larger width. I'm DYING for them to release the rumored 17mm PC-E (if that ever happens). And I only sold it to free up some cash at the time, it wasn't that bad.
Besides that example, I think the more important factors in lens quality are auto-focus, VR ability and quality of out of focus areas (bokeh). I came home from a portrait shoot the other day to find that my 24-70 was back-focusing on many shots. Me? The lens? The D800? not sure. But sharpness means absolutely nothing if the intended focus point isn't made!
Also, if you're shooting tripod mounted, large DOF shots such as architecture or landscapes, just use DxO to convert for maximum sharpness in the first place. I tested the 14-24 against the Zeiss 21, and standard LR conversion has the Zeiss sharper (only on the extremes). But once the 14-24 was converted in DxO, it surpassed the Zeiss. Meaning, paying all the extra money a Zeiss isn't always necessary.
BTW, quality of light is a million times more important than sharpness in any photo.... just saying