As another user stated, you're new to MMO's arent you?
I played and still play a Paladin in WoW. Vanilla, BC, WOTLK and now Cata paladins are completly different from one another; my class is pretty much remade every xpac, but yknow thats how these games work, things change all the time; sometimes good sometimes bad.
If you cant handle that, then perhaps a MMO is not the game for you.