I have to say I'm pretty excited about this one. So far it looks like they have held onto a lot of the aspects of L2 that I like and hopefully they have taken in what the last few years have taught them.
As for people wanting more out of their characters I'm not so sure about that really. I think it's both a strength and a weakness in WoW. While it appeals to the more casual players it is often a source of annoyance for others. There are many of us that would rather our tanks be tanks and our healers be healers (and thats said as someone with 2 fully heal speced chars atm). WoW classes started out with more clear definitions but over the last couple years it has sort of become "World of Hybridcraft" as Blizzard strives to allow players to do whatever job they can spec for with equal proficiency compared to main classes instead of their initial "jack of all trades, master of none" approach.
The Asian market games appeal to a slightly different brand of player and you are right that part of the market won't be happy with the setup. Thats ok though, not everyone is totally happy with what WoW offers either. In the cast of the Korean NCSoft games the Euro/US markets won't make or break them, they have so much support on the homefront that we are more of a side market that tags along on the Korean coat tails (for better or worse). I do think that if Aion reflects at least what they have done with L2 since NA release then it's popularity will be much larger than L2 ever was. Even L2 if time could be turned back and the current state of the game be the starting point I think the english market success would have been much higher.
At any rate, omg is it pretty. O.O