I played through the Beta as a Barbarian and a Witch Doctor and went through part as a monk. The game isn't bad. I like it. I don't see myself playing it as much as Diablo 2 though. Simply because once you get one of each of the characters you are done. With Diablo 2 you could essentially make 2 or 3 different necromancers by changing what skills you took through the game.
I think you hit the nail on the head, but I don't want to believe it :(
For those who didn't play the public beta this past weekend, the way d3 approaches skills feels very promising, at least to me. Every active skill for every class has FIVE skill "runes" that are unlocked as you progress throughout the game; each rune with a different (usually more powerful) effect.
For example, the
Wizard's Shock Pulse is unlocked at lvl 3 then skill rune Explosive Bolts is unlocked at lvl 9 which adds/changes the skill, then Fire Bolts is unlocked at lvl 18 which adds/changes the skill, and so on... This concept is so refreshing because it promotes going back to skills that you normally would NEVER use again in the later stages, unless of course you just want to have fun :P
On the other side, I'd assume that a maxed level 60 Wizard will probably have a sweet spot combination of spells that are very popular, but even then, hopefully the game will do a great job of making you adapt to certain situations and/or work as a team to take down tough elites/bosses.
EDIT: the catch is you can only have ONE skill rune assigned to a skill at one time, so you must choose... choose wisely!