Chargers were missing a lot of players when the Raiders beat them. Still took what 3 (or was it 2 I don't remember) blocked punts to beat them in the first game.
If SD returns everyone, they should on paper be pretty good. That being said Gates has been dinged up a lot lately and with the new CBA in the works, there's no guarantee Floyd or Jackson will be back at the WR positions.
As far as the Raiders ratings, I tend to agree that they are rated low there's some talent on that roster. I think they lack depth and have some holes, but at the skill positions they look pretty damn solid. Ford is a nightmare to cover, Miller is probably one of the most underrated TE's in the league, and McFadden and Bush represent a nice 1-2 punch. McFadden finally showed flashes of being the player everyone thought he could be when he was drafted. I am a huge Michael Bush fan. I so desperately wanted the Chargers to draft him. He reminds me of Marion Butts with his running style and his physical makeup. He's a presence and can wear down a defense, who's usually already tired after chasing McFadden around the field.
I think KC caught lightning in a bottle, I am not convinced they are quite as good as their record indicated they were.
Just going on talent on paper I would rank the Raiders #2 behind the Chargers, if the Chargers do indeed keep everyone and Gates remains healthy. If not then I think the it's anyones guess.
Phillip Rivers however does give the Chargers the chance to win any game. His production last year despite the fact that the Chargers were literally signing guys off the streets to play WR was pretty phenomenal.
I think the top 3 in the division are pretty close together the more I look at it however.
I will say this about Routt, I didn't watch the Raiders a ton last year, but San Diego had a lot of success against him. Malcolm Floyd had a 200 yard game, and I think IIRC a lot of that was on him. Rivers threw for 700 yards in the two games they played, and they picked on him quite a bit in those games. If memory serves.. I may be off there, as I have tried to block last season from my memory.