A new branch should be started in order to prepare for 8.4.0 AE API changes

No, it will only be done when it's at least beta or stable, I simply don't have the time to track every version.

Can this issue can be reopened now that 8.4 is in beta and quite stable?

better

I don't know if this can be usefull for you, but here's my crashlog when I try to start with the latest current release from AE2 (v.8.4.0):
https://gist.github.com/Fireztonez/75fe5ba5ed71d30ec83970b90952f35a