I got 2 LMGs from just matchmaking in DZ, don't even have a headset hooked up to my xbox one and never had a problem. 50% of the time you'll get in a retard group that is just AFK or whatever but half the time you'll get in one that is just PVE farming in dark zones. You just go from fist on map to fist on map killing PVE mobs, extracting when needed although honestly with how shit all the loot is I wouldn't even bother extracting loot unless its the LMG, the only loot worth keeping will be from the DZ caches. Thats the other benefits, you will be RAINED down with DZ caches (after you hit DZ level 50, which takes 4-5 hours?) as its only like 18k xp per DZ cache and you will hit that every 30 mins or so vs the 1-2 hours/level for regular PVE.
Rarely you'll run into a DZ with 4 people who are spawn camping/killing other players, I just logout, wait 2 mins, log back in and rematchmake and i'm in a new DZ without those people.
Since matchmaking tries to matchmake the zone closest to you (for DZ) I'd move first to the DZ gateway of the one you want to farm. It only drops from named Outcast bosses I believe so go to the one that has outcasts in it. I don't really get how often the DZ changes to conflict mode and other stuff, it seems to rapidly change often.
The LMG is total shit though anyways, garbage damage and the debuff is cool but lets face it if an enemy mob is standing around close enough for it to really matter you can just chuck a grenade at them too.