How to get StoneSense to work

Seems like a known bug to me, according to the Dwarf Fortress Forums

Once dwarves start training in a barracks, they will never ever do any civilian work ever again. No matter what.

Moose Men and Women, like their Moose kith, are dangerous due to their size, but won't go out of their way to get your dwarves, either. (Unlike the evil, evil Honey Badger)

This is a very literal case of "they're just as afraid of your dwarves as your dwarves are of them".

However, it sounds like your dwarves may have accidentally cornered a Moose Man or several, and, like all cornered creatures, will defend itself vociferously. Since you have several dead dwarves on hand, it's likely that they simply wandered too close for their own good.