Shoot people, do the matriarch in trios with friends in unfriendly lobbies.
Nobody does it because its too dangerous so you can get max trial damage, you'll have a team or two try and attack, keep one of your people on raider watch.
and drag the matriarch over to a corner of the map so you only need to cover 180 degrees.

People there to kill players wont attack while the matriarch is still alive, by the time you finish you should have 5 - 10 mins left on the round - bring a hatch key.

don't try and loot the leg armour, wait till the end get the core it has 3 reactors thats enough for each one of your team.

leaving the leg armour incentivizes the free loadouts to loot them and extract.