I agree that we don't know what Blizzard would do about a widely used program that hooks API calls in the sense I described. I think it's possible that they don't know themselves since, like any company, they probably make most of their decisions when they have to take some particular action or other.

But we do know what the EULA says. Which is not say it's easy to interpret. Nobody would be happier than me if I'm interpreting it wrong. I could write better software if that were the case. In the meantime, though, I feel a responsibility to my users to read the EULA as carefully as I can and stick to a conservative interpretation.