1. What exactly is going on? 2. When will it be fixed?

In the middle of a crisis, saying "we're aware of the problem, and we're working hard to fix it," for hours does not really count as communication. It increases customer aggravation rather than decreasing it. Customers want to know answers to the above two questions. They don't care that you know about the problem and that you're working on it, unless you're not doing those two things in which case they will be (and should be) furious; those two things are expected.

Barring the ability to tell your customers "we will be back up at X:00", I think the best approach is to share as much information as you can without getting into proprietary information. That's why I think GP considered their communication a failure. That's why I consider their communication a failure, although I've seen this pattern enough from different companies that I don't hold it against Heroku as long as they learn from it.