Chewman, I get the impression that you have yet to play Brawl for an appreciable length of time. If this is the case, I wager that your opinion on Zero Suit Samus will change after you have logged some hours on the game. As for your other points, concerning the matches between this Azen and Chillin, that doesn't mean anything. A single (or several) random match you saw on Youtube doesn't "prove" a character is good, regardless of the participant's supposed mastery of Melee or whatever.
As for the Yoshi thing... I'm sure this has been gone over quite thoroughly already, but I agree that he is definitely one of the worst in the game. I wouldn't say the absolute worst at this point, but he's pretty mediocre. For sure, they increased the viability of his special moves, although the up special is lowered in utility as a projectile. His recovery is better, but good recovery doesn't mean as much in Brawl as it did in Melee overall. The good news is that a number of his moves are better now, relatively speaking, namely his backwards aerial, forward and up smash, and in my opinion, the up aerial. But all in all, he doesn't have enough strengths to peg him as a competitive character, at least not with the current known techniques and whatnot.