I've used AR Giros quite a bit and here's the thing about it:
W3 isn't bugged... it just doesn't hit when you're right next to the enemy. Instead you'll want to use it from a little distance away. It does control shock and doesn't knock down, so you can sort of use it to confuse the enemy... if it weren't for the fact that the animation takes really long to cancel. On the other hand, it deals good damage and reloads relatively quickly.
W2 is just a regular shot lancer. It doesn't have too much ammo, but when giro's assault command turns on, it does quite a bit of damage. I'd say to take advantage of this when you can.
W1 is pretty average. It cancels pretty well, but doesn't really have any vertical reach. You can perform SS/ZBS with it pretty easily, just don't treat it as if it were Sword Calamity/strike/impulse/strike e
Combo wise, you can try to combo w1>w3, but I wouldn't recommend the reverse due to w3's immobility. On the other hand, you can usually get away with a W3>w2 combo as long as you make sure you can pass the enemy while using w3.
Skill wise assault command lets it deal decent damage once it gets activated, even if you're just using the shot lancer. The vet infighter skill also protects it from being killed from too far away.
It's also just got melee sp.
Does this help?