No.
DC fans are just throwing a tantrum. The fights weren't even close. He lost 4 rounds to 1 in their first fight and he was losing the rematch before getting KO'd in the 3rd round. The skill gap was just too big to fully blame on roids.
It's like saying Shogun would have beaten Jones if he was off the juice. Juice or not, that version of Shogun was never beating Jones. They were on different levels at the time.
It doesn't matter how much Josh Barnett juiced, he was never beating Crocop. Roids cannot erase such a big skill gap.
Now the Gustafsson fight is another story. Gus has a much better case than DC because his fight with Jones was actually very close. If Jones juiced for that fight, then it's reasonable to think he could've lost being clean.
I'm OK with DC getting the belt back, being ranked #1, etc. But saying he would have beaten Jones? nah, that's reaching. Nothing I've seen from DC suggests that he could beat Jones. The version of Jones that fought OSP would have still outpointed him all night.