There is a way to have a session to yourself for at least a little while. One person disconnects his internet for a moment and ends up in a solo session, he then invites everyone to a mission and you will all be in that session with no other players, if you can get two groups as rivals (even if you aren't fighting each other) you will have less NPC's to contend with in those missions.

Windows 7 64 SP1
Gigabyte 970A DS3P FX
AMD FX6300 Vishera 3.5 Ghz
EVGA GeForce GTX 760 SC 4GB
16Gb Kingston Hyper Fury X 1600Mhz
Onikuma Gaming Headset (has annoying blue lights I don't use)