This does not appear to be a total outage. I cannot reach any of our sites, and Pingdom also reports we are down, however, I can see normal looking traffic reaching our servers (via heroku logs --tail). In addition, members of our team are reporting via Slack that some can reach our Heroku-hosted sites, others cannot. It seems to be ISP-related. Two people within 1 block of each other on different ISPs see different results.

We proxy some services through Cloudflare to gain IPv6 support, and all of those are down, which suggests the Cloudflare -> Heroku network route is broken.