Dexter is one of the laziest MoFos in Pro BB, trains like a granny, does no cardio, and dieting for a show for him means to order his hamburgers without cheese (according to Markus Ruhl). Dude is a genetic freak with an exceptional response and tolerance to longterm drug abuse.
Lazy? You don't go from being a bantamweight to MR. OLYMPIA, by being lazy. I don't care how much of a "genetic freak" you are or how much "drug abuse" you claim.
And you certainly don't stay among the best in the world for as long as he has by being "lazy", either.
As for Markus Ruhl's comments, as Ruhl has all but disappeared from bodybuilding, those comments are probably old. The Dexter Jackson of yesteryear got ripped without cardio. Dex and his trainer have clearly stated that the 40+ version of the 2008 Mr. Olympia has to do cardio to get himself in shape.
BTW, Ruhl would also be a "genetic freak" with "exceptional response to long term drug abuse". Yet, he never won the Mr. O. In fact, he consistently lost to much smaller bodybuilders, such as Jackson and Darrem Charles.