when you say mk2 do you mean canon 24-70L II? if so I think you just verified you are crazy anyone looking for optical improvement over that lens is on a pursuit of insanity, and just look at the price and size of the sigma. I think there's a stronger possibility that sigma laid another egg
Talley went to NYC, visited B&H, and bought nothing. He even posted a photo of the nothing he bought! I think that qualifies him as certifiably, and completely, insane.