Yeah -it's just like he uses his Intelligence score in combat!
Actually, I expect my leather strap would break before my neck would.
My arming cap does not cover my face, nor does any I've ever seen. Do a google search of "arming cap" and you'll see dozens of them.
They jumped on him all together, which is the best way to quickly defeat a dumb barbarian who never uses magic items, but plays into the hands of a smart warrior with lots of items and tricks.
(Besides, if they knew it was Tarquin, they have a potential hostage. Somebody - maybe the genre-savvy bard - could put a blade at the throat of Tarquin's son and demand that Tarquin surrender.)