Honestly though you do not want to use your taunt that often as it does not increase your initial threat. What the taunt does is place you 130% threat above whoever currently has threat. Which in all honesty you would think it would increase your threat by 130% but since you are already the highest threat on the target it does not.
That was true for World of Warcraft, this game has different taunt mechanics. It works the way other posters pointed out.