A Slot Grima Robin

Steady Stance is a really good option, as well as bond skills such as Atk/Def bond, and close or distant def, sadly all of these are from 5 star only.

Inb4 Distant Counter.

I'd personally go with Close Def or Earth Boost, so that he has an easier time against Falchion.
Or, like Poofinator said, Steady Stance.
EDIT: I'd definitely go with Close Def myself, since I have like 2 Sigurds I'll never use.

It depends what you want to do really, options like Fury, Close/Distant Defense and such will give him more defenses to work with, which he'll appreciate.

However, if you wish to go with Breath, I'd suggest rolling for Hardin: with the QR seal, Robin will be a potent force on Player Phase with Bold Fighter, and on enemy phase with the dc qr combo, which will only be furthered by Steady/Warding Breath.

I put fury on all my drags except Myrrh which has DC so ill probably go fury.

I'd personally go for Distant/Close Counter, Brazen Def/Res, Earth Boost, or Fury. They all seem like fairly respectable options for him. Or, I mean, you could go for Steady/Warding Breath, and just use Vengeful Fighter as a beefed-up QR.