AFAIK resque 1.22.0 is pretty old. Resque-scheduler has to be downgraded from 4.3.0 to 2.2.0 just to support is. What reason is there that Heroku requires Resque at 1.22.0?
Apologies for answering my own question. It appears @Pavan was right. I'm running resque 1.26.0 right now with no problems. Perhaps I should update the link on Heroku to >= 1.22.0 ..