ex-Heroku here. The codebase is sound. I would almost certainly expect that the reason for the slowness is the ability/diligence and paranoia levels the SFDC

ex-Heroku here. The codebase is sound. I would almost certainly expect that the reason for the slowness is the ability/diligence and paranoia levels the SFDC security teams have. They won't want to turn this back on until they are absolutely certain it's 100% again.