Heat is a console emulation and has been talked about on the DUC for many a time. I suggest you do a search to find out what it's all about. And Eleven is a guitar amp simulation - again check here on the DUC. Or make Google your friend to check on them both.
There's a difference between what's considered compatible by Avid and what works. For quite a while I had PT 11.3.2 running on Sierra OSX 10.12.6 with the only issue being to import audio I couldn't use the menu option but had to drag in audio via OSX Finder. It's probably the same for you; I'd suggest making a bootable clone backup of your system (you do that anyways right?) using a program like Carbon Copy Cloner. Then either partition your system drive and put Sierra on that and test out how it works for you. Another option is that instead of going up a level in OSX to go down a level to OSX 10.10.5. OSX may or may not be the issue but either way El Crapitan really should get ditched - you'll find no love for it around the DUC. There's a reason it's called what it's called and it isn't good
