I think Pippa, our cocker spaniel, probably wouldn't notice what was going on. She lives in her own little world. If she did notice, she would bark and egg the other dogs on if they were there while keeping well away from the action herself.
Our Irish setter cross, Amber, would definitely protect us. We were cutting Barney's nails the other week and he hates it to the extent we have to muzzle him and it's a two person job. He was making a bit of a fuss and Amber must have thought he was attacking us. She was straight over to sort him out, poor boy. I'm sure if anyone went for either of us, she wouldn't think twice.
I think Barney (basset fauve) and Joey (pointer) would wade in too, especially if Amber took the lead. Joey on his own might not be quite so brave.