I'm not familiar with the super heavies... but are we missing out on some incredible 300 pound talent that can't make 265? Any names? I'm curious. Seems weird to cut off the weight class like that... boxing has no such limit on heavyweight, correct?
Nope, but mma can't have a limitless HW div like boxing because of ground work 
No one that would be relevant in the HW division.
Hopefully someday we'll know. 
Big Monster Santos
Good to have a limit, it forces them to get in shape and have some accountability.
I've been preaching for a long time on here that the heavyweight limit in MMA is utterly pointless. Do we really need to protect Dos Santos, Cain and Overeem from the likes of Hong Man Choi and Bob Sapp? Name one top 20 heavyweight that would fight above 265. The only guy I can think of is BigFoot who might fight around 275.
fannypack - theres some big 300+ dudes, Karelin was at 325 all natural snatching gold like a monkey
Karelin wrestled at 130 kgs / 286 lbs
I think the cut off isn't needed, look at Pride's heavyweight roster and champ....