The military is as buggy as it was several versions ago - nothing major has been fixed yet. There is exactly ONE way to make it work:
1) Make all the equipment you need
2) Draft dwarves, making sure none of them have "lazy" descriptions in their status
3) Designate a barracks for 'T'raining and keep your squad inactive
4) At this point, some dwarves may have been assigned two left gauntlets or two right gauntlets. To re-equip, disband squad, clear barracks designations, and repeat steps 2-3.
If you try to re-equip by just assigning new equipment in the military screen, they either won't pick up new equipment at all, or will end up with ridiculous stacks of equipment held in a single hand/foot/torso.
When you want to attack, use the "move" command instead. This will be a pain against any enemy that moves around quickly, but at least it works.
My current fortress is seven years old, and has had the same three steel-clad axedwarves defending it the entire time. My only other defense is a line of three cage traps across my entrance for catching thieves and snatchers. I had to disband and remake the squad a few times to get lucky enough to give each dwarf one left and one right gauntlet, but I've had no trouble ever since. Their notable kill counts are currently 23, 49, and 123 (roughly correlated with their armor user skill, which lets them get into fights quicker and run down more fleeing goblins).