I have the same problem and there is still no solution.
The thing is I want to mix into my masterbus. I think thats a typical way of mixing nowadays. so, if I send my subgroups (dr, vocals, ...) to the analog summing mixer and the summing master out back to the DAW I have some delay witch can not be compensated. And it is improtand to compensate it, because I use automation on the mixbus (after the summing in the DAW) and so it is important that the summing return isin sync with my session.
The only way to compensated (nearly sample sync) is with I/O inserts. but in a summing szenario you should have a 8 or 16 I/O insert to tell the ProTools whats going on. And there is no option for Inserting multi channels of 8 or 16.
the video with Fab is showing how to setup the 2 bus.
https://www.youtube.com/watch?v=0gW18nrUJOI
but his print track is delayed and he is not talking about that problem.
I dont understand why there is no solution in ProTols to compensate summing I/O
monitoring the analog out of the 2 bus makes no sense in a mordern mixing szenario.