EQ1 did this with AAs, EQ2 did this with talent points now with vanguard we have to wait till they launch talent points.
IMO Talent points are a crucial part of any mmorpg not only does it allow you to build almost new classes but it brings huge diversity for example we will take WoW.
Priest can either be a shadow priest or a holy priest we know how much different they are almost like two whole different classes.