Hamedo doesn't work on monsters, so it's best to equip it when you fight some story battles. It does work on Zodiac bosses, like Velius. I killed Velius with Hamedo. And yes, a long range weapon user with hamedo might kill, but I don't know if it's effective against short range users. I think if you use a gun and you have hamedo, you might pary all of Balk's attacks.

Yes, that...guy... Balk. I hate his guts, because he has long range and he's a sniper.