the replacement for the 5Dmk2 is the 5Dmk3. the 5Dmk2 is end of life and it was never considered by canon for it to drop in to lower class type camera. The reason it was on sale because they have new stock, what's the best way to get rid of stock, keep selling it until it's gone.
the 6D is designed for experienced enthusiast/hobbyist type person that is after full frame. it's not a FF rebel/60D because if it was it would be made of plastic, have a flash and have the auto modes.
Everyone likes things linear but that's not the case. Even canon say this.
Why??? so you want to see a fault and you take a photo that shouldn't be taking in the first place and push it beyond what one would normally do. You should always get correct exposure in the camera first.
This is an absolute joke. End of life? In terms of technology? Arguable. In terms of capability to produce beautiful images, not at all. Remember that this argument that the OP has presented is his FIRST DSLR. He cites no prior photographic experience or etc.
5DMKII is more than capable. Hell a 5D is more than capable but lacks the desired video capabilities. This is literally a spec pissing match that will not lead to him taking better photographs but just having great equipment.