Armsmen does what it always has done. It's just that Armsmen really shouldn't be classed as a tier 3 talent. It just becomes so expensive that it's not worth taking over the 2 or 3 weapon trainings it would take to mimic the gear you would ever find in your character's lifetime (beyond the 3 the character already ahs to have as a part of its pre-requisite). It almost should be a tier 1 talent, as its still ultimately sub par to taking the trainings. That said, it has its uses.
I agree, it was only useful in DH because some classes didn't have those particular weapon talents in their tables at all. Armsman could be a suitable substitute in those cases. It really isn't even necessary in OW, since weapon talents are so cheap and unrestricted.
My solution was just to throw the Heavy Weapon training talent out (since it wasnt even properly printed in the book) and go with allowing Weapon Training (X) to allow you to use all weapons in that category (Heavy, Basic, Pistol, etc).