Personal opinion -- way too powerful. A couple of levels and he will be negating everybody's armor. And basically removing everybody's DB that he is fighting against.
I don't think you should ever allow a talent that lets somebody ignore a foe's DB.
If you are using Martial Law, you could perhaps have a talent that reduces the armor adjustment by one step. (i.e. if foe is wearing chain, and you adjust crits according to armor worn, then that foe is treated as Rigid Leather for that armor adjustment). Or something along these lines.
And it should also be on a per weapon basis (in addition to any other limitations). This is not something that should be usable with all weapons. If it is special training, then it is training for a specific weapon.
You could make it be something like each time the talent (which costs a minimum of 20 DP) is taken (for a specific weapon, against a specific type of armor), the character gets a +5 OB for that combo. Can be taken multiple times for different combos, but the bonus used in a given attack can never be higher than the DB provided by the armor.
This can be a game-breaking ability. You need to realize that before you go any further with it.