Cheers! I’ve got the load time down quite a bit by changing the vagrant config to use NFS file sharing.
Originally I was incorrectly using the discourse docker image for dev work (which had the 4min rebuild) instead of vagrant. Apparently it is possible to use docker for discourse dev work, however the discourse docker image is designed for production and not dev, hence my issues 
Discourse running in vagrant lets me make changes and simply refresh the browser to see them. It takes about 20 seconds to refresh the page after a change, but after that it runs nice and fast.
Others have run into this issue and the only fix is to skip vagrant and run it all locally. That seems to fix everyones slow discourse dev problems.
This ruby and ES6 is all brand new to me so I’m limping through it in my free time I’ll give it another crack tonight.