http://www.eventhubs.com/tiers/ssb4/ I believe this is the official list. Last time I was on this site, Rosalina was top tier, though that was when the 3ds SSMB was out.
I'm not surprised, honestly. I was already seeing that when it came to the competitive Smash scene, that Melee would be the go-to game. And as for the tier list, I guess that's the closest thing we have right now, as most "official" Smash tier lists are made by the Smash Back Room.
Yeah, Diddy is top tier. He was already high tier in Brawl, so this is not a surprise really. Also didn't expect Yoshi and Sonic to be so high on the list too.