Oh I am having a great time playing my infiltration shadow atm. Most of these rerolled snipers/slingers are very bad, and they are the easiest kill in the WZ. Nothing to do with the class being bad, it is just they have no idea what is going on half the time.
As far as classes? You can play them all after the first one. Legacy gear, pvp dailies makes this possible. The gear grind isn't bad at all. You don't HAVE to play just one class in this game. This isn't WoW, you can actually play a lot of alts and have a life. Which is why I like this game.