I disagree.
the impression I have is that the Stealth Armor isn't for while you're in combat, its for making a getaway, or getting into position. Perhaps the AC models you can fight with the stealth active, but the A and B, you don't want to sacrifice a single MP if you can help it, you need every little bit of your TMM that you can generate, and running the wulfen up into the red is going to prevent you from achieving that.
Plus, if you're playing with the advanced ECM Rules, Ghost Targets works better than Stealth Armor for the Wulfen. Sure, theres a chance you won't get the modifier, but there's no heat involved.