Meshuggah - DEI also. To me heavy means other things than what most people i think would say. I don't find Cannibal Corpse, Nasum, Dying Fetus, Suffocation, Cryptopsy heavy. to me heavy has to... i dunno kinda groove. Another notable heavy album to me is Machine Head - Burn My Eyes. Really i say that in all seriousness.
When I saw this thread, I thought you would say Meshuggah - Destroy, Erase, Improve. I don't know why...I guess because I would probably have to agree with you. I think it's very heavy, but I am not sure that it's the heaviest album ever.
It's easy to make a "heavy" album with all the fancy recording devices and stuff nowadays, but I don't think anything tops this piece of pure chaos from 1986.