I don't think fedor is that badly declined, I mean he was head and shoulders above people for years, and those people are STILL top 10, plus he didn't take much damage - he was tko'd once - guys like Mir and Arlovski have been tko'd and KO'd several times, and he wasn't in a lot of brutal back and forth wars
I think people hold him to an unfair standard, he lost to werdum... everyone is losing to werdum these days and he was doing pretty good against Hendo who hits like a truck and has a lot of wins over a lot of great fighters from 170 to 205. So he really only has 1, maybe 2 "bad" losses. If you look over the UFC top 10, outside of JDS and Cain who hasn't had multiple "bad" losses- Hunt has a .500 record and was knocked out by a middleweight, Arlovski has been KO'd like 10 times and had a couple close fights with journyman, Werdum spent 3 rounds crawling on the floor against Overeem, Overeem has been knocked out by several people. Crocop has looked like a shell of himself for years and still gets wins
If these are the best heavyweights the UFC can find in an entire world of people trying to make a living doing this, Fedor is certainly capable of staying in the mix, the issue is if he loses once people will scream "EXPOSED!" but then not bat an eyelash when UFC "greats" like Mir and Nog are looking terrible every other fight.