I was on the Battlefield today and attacked another squad, and discovered that their Regenerations were cancelling out my Blinding Attacks, something I'd never been aware of before. Does this mean Blinding Attack is essentially useless against squads with any kind of species-specific defense, such as Song of Peace, Plates, or Scales? 

From the Tactics FAQ -- The opponent can't score any defense points for this attack. Does not trigger Hold the Line when used by a GP3 pet with 20 tactic wins.

So, from what I can infer, it means that if it's facing a defensive tactic, then that tactic is counted as a Wait instead.

I assumed that was how it worked, but Blinding Attack is the only attack move I was using, and the other squad was gaining defense points. 

Here's a screenshot of the battle. http://imgur.com/Q0enywa

Hmm, some of it is rather odd indeed, such as the wait leading to 1/2 and regen scoring 2 when your attack only scored 1, shouldn't be possible if what the tactics page said is correct.

What was that pet's species, or who was in that team? Might give us an idea of what's wrong. (From what I can infer, it was counting the whole battle, rather then matching each roll to each other, and if it is, I won't be of much help, since I don't pay too much attention to details.)

The opponent squad contained two unicorns, a roc, and a dragon. My squad consists of two unicorns and two dragons. The only explanation I can think of is that they were scoring defense points for my Blinding Attack, in which case Blinding Attack is far less useful than I'd previously thought.

Yeah, that's probably the case, might want to submit it as a bug, since it's most likely one.

Ps. I remember them (Blinding Attack, Petrifying Gaze, and Battle Cry) being 0 attack before, so they might have been changed, but it also caused them to loss that negating defense ability.