The 'one incident' was the AWS outage that brought much, much more than Heroku down, and their post-mortem was fairly impressive, as far as that sort of thing goes.
I'm not saying you don't have a point, but imo your comparison of Heroku's 76 vs. Tumblr's 42 is not apples-to-apples. I think you have to at least put an asterisk by the 76. What OP is complaining about is a early-Twitter-days-like unreliability over a long interval, not a one-time outage that has a single explanation and for which Heroku took completely responsibility.
For my part, at the moment at least, I still have more confidence in Heroku than Tumblr, 76 vs 42 notwithstanding.
I'm not saying you don't have a point, but imo your comparison of Heroku's 76 vs. Tumblr's 42 is not apples-to-apples. I think you have to at least put an asterisk by the 76. What OP is complaining about is a early-Twitter-days-like unreliability over a long interval, not a one-time outage that has a single explanation and for which Heroku took completely responsibility.
For my part, at the moment at least, I still have more confidence in Heroku than Tumblr, 76 vs 42 notwithstanding.
https://status.heroku.com/incident/151