Well, protestants have no church to speak of so the fact of them not having a bishop is a moot point.
In Orthodoxy a bishop is just a priest with more duties. It is also the duty of any lay person to call out their clergy if they veer off into heresy. It's a duty of a priest to disobey a heretical bishop. Since the beginning the church delt with heretic clergymen, small and big scale. Ones salvation is not dependent on a bishop or a priest, if he falls into heresy you search for the one who is keeping true to the church teaching. The church has been over this times and times again and it's still here, after all we were promised it would till the last day.
No because the laity is only obliged to follow the church fathers, apostles and God as a paragon. The truth once given. If Samsu comes up with a teaching contrary to them it's he who's in trouble.
Talk about judging a book by it's cover. Well, monks at Hilandar think otherwise.