While Taunt has always been intended as a core tactical mechanic, a lot of discussion last season was given to how it could be abused, particularly by fighters with Battle Presence. I've decided to revise it as follows:
Taunt
The action forces the affected character to attack the user to the exclusion of other targets. The effect ends when the affected character is attacked by a character other than the user, the user is incapacitated, or the end of the current encounter.
The only change here is that a Taunt breaks when someone other than the user attacks the affected character. Thus, forcing a monster to stay on one character will either require coordination between party members or constant reapplication of Taunt.