Onslaught Mob Variances

So, I was playing Onslaught with my boyfriend and we would continuously reach the level where you have to move down the road in the circle with all of the firing away at you, effectively making it a bullet hell shooter. We died at that level and wiped at least 5 times with different randoms. I ended up learning how to play Poppy just to try and get somewhere, we came up with game plans and strats.

Then, on the 6th try, we got to that level and... There were no It was basically just a bunch of with a few sprinkled in... And it was SO EASY. Are the levels random? Was this a result of our team comp? Honestly, I have no idea, and neither did the 3 randoms we were matched with. I built a ton of MR thinking I'd have to deal with them, but no.. I noticed a variance on the map with that you have to run around too. The one with the fencing in the middle and such.

I'm curious if you can get a 5 man and just "farm" the levels. Just all surrender if you don't get the right ones. Kind of like "farming" for perfect greater rifts in Diablo.