I don't find it exploitative but rather artificial meta gameplay. I don't like such tactics (that's why I don't play Tactician).
Anyway, it has nothing to do with taunting. A taunt is quite useless if blocked by armor. When armor is gone on all targets, the fight is usually over quickly. I would opt for armor ignore for taunting. We already have a very annoying exception of armor ignorance in the case of oil (I really do not like this), make another for taunting, in this case even with some sense in it.
