So here's my input. I have done it 5 times. they were all in a row and all in PUGs. First got to 15/15 and wiped, team broke.
Next were 4/5, 8/5/, 5/5 and then we finally beat it. (All teams broke up after the first wipe)
I'm a casual player, don't glitch etc. I went in to it not knowing how it even worked. I was at the time GS 168, DPS 115k 65k health. I was running first aid and pulse.
So my first run, I had no idea what I was doing, just shooting stuff. They stayed at the far back right corner for most of it.
The other groups all went immediatly to the trench in the middle.
When you first try it, I would literally just try and stay alive, most likely the other guys on your team have an idea about how to get the bombs and hit the APC. Everyone doesn't have to do that part. Stay out of the red, try and kill shotgunners, drones and provide cover when someone goes running up to place a bomb. Once you get a little more comfortable, You can try the bomb runs yourself if you want. After a few runs, you learn the mechanics and it gets a lot easier even if you do fail, you know what is going on.
EDIT: I should also note, I was in all yellows except the mask/knees which I crafterd from the striker set and my pistol was purple,I was running the high end AK and the vector. (I really think longer range weapons would be better here, so marksman and SMG maybe, but I can't get a good roll on an M44 and the mats grind is a bit nuts now for a casual player. I Also should note I got 2 tactician holsters as rewards for my only win, better than my yellow, but not good for my build.