Yeah, no. I would only shoot them if they started biting me. Most dogs would not do that, though... even off the leash. That said, I would make sure the owner paid any damages for not keeping them leashed. It is the law, after all.
If you choose to let actual harm occur before defending yourself, that's your business ... but in general, one is not required to allow himself to be harmed before engaging in self-defense. Reasonable belief that harm is about to occur is generally sufficient. IANAL.
I would shoot them to prevent them from biting me.
If two pits manage to grab a hold of you then you won’t be shooting anything.