rerolling takes far more effort this expansion, just because grinding those artifact perks back costs a good amount of time. But even now it's absolutely possible to reroll, perhaps mythic raiding won't happen if important perks are missing...but other than that you should be good. Why keep on playing a class or spec when you obviously would have more fun with something else? The longer you wait to reroll, the bigger the "drawback" gets. So just do it now, have fun and don't worry so much about the "what if".