Yea im from L2 aswell and i had/have the same worries you are expressing here. Honestly im hoping these current classes are like the lvl 20 class changes in L2 and the lvl 40 classes will come at a higher level later in the game, but i kinda doubt its gonna happen.
As for the pvpve, i think its going to be an awesome change, i really hope the baalur are crazyh strong and pound us like babies
or the will be worthless in end game (like the seige NPC's in L2).
The faction based pvp is cool because we can kill without consequences (karma) but without trash talk/polotics i fear it wont be as heated as pvp was in L2. Hate needs to be involved if even at a minimal level between both sides in a PVP or its not nearly as fun.
P.S This is just IMO
Oh yea i almost forgot. As far as content. The world of aion apears to be HUGE from what ive seen, not only from a xp/questing POV but also taking in the fact that you can fly, so very little should be "off limits" compared to other games. Abyss FTW