If you had waited a bit longer they might have pushed themselves and been forced to flee/regroup or at least rest up. That's the perfect time to pounce when there's a bit of chaos.

This can be more difficult with the Bard maintaining health but when the Bard rests you at least know he's drained.

I'd also focus the warrior first too. You have cold damage vs. a Fire Giant and he's not going to tank well, you might do enough to kill him or spook him before finishing the Bard.

The Bard on the other hand just tanks like champ and stands there whilst the Giant beats you down.