I expect it will take me several months to hit the level cap. As with all MMO's the focus is around the end game.

I have no idea what the end game is like in AION personally but if my assumptions are correct there will be plenty to do with an active guild.

End game is focused on PVPVE which means guilds can siege and claim keeps from NPC characters while also fighting against the other faction.

Or just hunt the opposite faction for Abyss points which like honor reward armor and weapons.

There are also instances and raid instances I believe where you can collect Abyss points, loots, and what ever.

If we are able to field 2-4 groups in the end game I suspect we will be able to compete without alliances in end game content.