So, by the time you hit 7th level, that's at least three attacks in every battle that are probably accounted for by your encounter powers and in some battles you will also use a daily. (Theoretically, someone might use a standard action utility power too, but most characters will not have them). If combats are typically 5 rounds, that's only two rounds of at-will powers--or three if this is one of the combats where you spend an action point.
And with regard to the wizard and the hypothetical +Int/+Wis race, remember, you're not trading the third at-will for +2 Wis; you also get a racial encounter power in the deal.
So, Humans are quite good for some classes/builds, not so good for others - which is true of all the races. Humans, though, can always manage a +2 to thier primary stat, so they can at least be viable with any class and virtually any build ('balanced' builds in split-primary classes, like the Star Warlock, for instance, are the exception).
No doubt there, but Half-Elves get access to all those wonderful feats too.Further, I still say they have some of the best racial feats...like action surge.
Paladins--The Class most dependant on multiple stats in the entire game. Avoid like the Plague.
I totally disagree (as a player of a human paladin in a 4e game). The +1 to all defenses for being a human stacks with the +1 to all defenses for being a paladin and you can throw being able to use plate armor despite having a low STR on top of that.
The only real down side is one useless At-Will.
When the Divine Power book is out, you will see the number of human paladins explode.