I suggest you two tone it down, as you are on thin ice here -> [Info] Handicap, Momentum, Scripting, DDA | EA Forums - 12392959
Now, as far as the actual difficulty goes, yes, it's pretty much unbeatable at this point in time. I managed to get past it a few times, but it's not worth the effort.
The key takeaway is that this has been raised, and it's being looked at, as the dev I spoke to was plastered by AI as well, so he said it needs fixing. When it will get easier (fixed), I do not know, but it's being looked into.
From my observations, it appears to be an unintended effect of the addition of playstyles, as nightmare games vs teams that have no playstyle cards are hard but beatable. Play vs an AI/PVE squad that has playstyles, it will ream you a new one.