I'm of the opinion that Provoke was designed the way it's working, it forces players to manage their enmity against the mob.
Parties are supposed to be a team effort and everybody need to know what their enmity threshold is and keep it below the tanks.
If Provoke gave tanks extra enmity there would be no reason to manage it in a fight.
We have a lot of enmity generating moves as it is currently.

Just my 2gil.