Symptoms of the WhatsApp outage smelt like they were using portions of the same infrastructure. Pure text messages would send, but image uploads would take a long time before failing. This is as though they were being uploaded to some Facebook image store that was not responding.
This was also the symptom of when the Chinese government was trying to stop certain photos of Winnie the Pooh being uploaded on WhatsApp. They just blocked any uploads of approximately the same size.