No, no one was bored-looking, that's for sure.
If they weren't bored, and if they were engaging with the encounter (rather than just "I swing - and miss"), then I would consider this a great outcome, even if the player dice went cold. So good job!
Sometimes if a battle gets into a repetitive cycle I'll consciously try to mix it up by having the opponent change its approach. I like to have opponents talk to their prey (er, the PCs), so after 2-3 rounds of complete failure on the part of the PCs, the dragon might hold its attack and offer mercy if they agree to serve it, with a healthy dose of taunting, of course. Or the dragon may get bored and try to snatch one PC and fly away with him/her. Or the dragon may just continue the same effective tactics but begin gloating about how it's going to capture them and eat them slowly, over a week, while their companions watch. The key point here is that you have one interaction (combat) that is in an uninspiring cycle. You can either directly introduce some change into that interaction, or you can introduce another dimension of interaction that can provide a diversion while you're waiting for the combat to get more interesting.