I just did the insider thing and now its installed in a normal folder. Its stopped the optimizing every load but the net code is still broken. The game runs fine but its boring without all the other players doing the pink circle things, I will try it again after the first DLC drops.Well, that's not normal.
I found the advanced install features in the xbox insider build have improved stability a lot. I had a hunch the virtual filesystem MS were using was causing a bottleneck as i was seeing some crazy high cpu usage by the filesystem when the game was loading assets and i believed that was a big contributor to the low streaming bandwidth issues i was having. The advanced install features does away with that filesystem and installs the game in a regular folder and i've had next to no issues now and filesystem cpu usage is gone. That's not a coincidence.
So yeah, if anyone else is having low stream bandwidth issues, right click the game in the xbox >> manage >> enable advanced install. It might help.
sidenote: this also fixes me having to allow the game through the firewall every other launch as it no longer mounts the game in some new pretend folder that the firewall doesnt recognise. It also means soundmixer now remembers my app volume settings for the game.