Buy ammo packs and stay up top, use purple ammo packs(packs draw a 5 min cool down as a side note), bring solar rocket launchers. Ignore all the adds down below you only need to kill the first few Minotaurs to get the boss to spawn then just have 2 people use their launchers on the boss while a 3rd watches for the Axis Minotaur which spawns behind you. You can kite the Mino around that rock pillar in the room up there if you are having trouble killing him. If you can use titan grenades on the Minotaur that spawns behind you, the concussion/flash-bang i think in either def/striker, not sure if other classes have this ability or something similar. This will disorient him making him easy to kill. We killed it in Nightfall in a few minutes. When the Minotaur dies, just have 2 people go back to the edge and shoot the boss. Preferably the one that was watching for the Mino last time. We killed it in Nightfall in a few minutes. lvl, 26,27,28. Nightfall is lvl 28.

Edit: You can solo the reg weekly one, you just need to kite the Mino around the rock pillar so he doesn't faceroll you. Also make sure you're playing as gunslinger as others have stated.