A recent response on this from Quickpaw in this thread.
I haven’t played enough of the higher difficulties to say anything too specific with confidence, but what I experience (disregarding of the difficulty) is that the difficulty spikes vary to a very high degree.
Certain missions or areas in missions become incredibly difficult if you have back luck with what is being spawned. My take on it so far is that it’s mainly
- open areas where you’re easily flanked, and
- if you get a high density of strong ranged units or a bad mixture of carapace armor tanks and strong ranged units.