Actually just to support The Mage King's crossed out text, you should probably tell the player with the Fighter to change their class. After all the Fighter is one of the classes that are commonly replaced by ToB. Warblade is a nice alternative if you want.

All in all, ToB is only something to watch out for relative to the rest of your party. Like you said, it starts out of the box pretty strong and if your other party members aren't used to that level of power tell the ToB player(s) to scale it down a bit.