That's damage resistance that can be cut through with a common metal. If we industrialize werewolves then anyone capable of standing up to them will industrialize silver weapons.
Even if that doesn't become a problem, they still go from AC 25 to AC 18 and lose their weapons at minimum. That means they lose any special weapon material properties and have a lower to hit bonus for all three of those attacks.
DR with an easily exploited weakness and extra attacks aren't worth getting hit more often and missing more frequently. This is especially true when it starts interfering with the tactics that make individual legionaries effective soldiers.
We're better off finding exploitable mass buffing spells like the family of spells based off of
Insignia of Alarm if we're seriously going to look into enhancing base legionnaires more.