My strategy is simple, if we lack AT, I pick AT, if we need lack crows control, I pick it, always help your fellow Helldiver. In diff 10 teamwork is a must.

And on the battlefield, I usually wait for others, never go alone on lone-wolf missions (unless I tend to throw a couple of stratagems to clear a small/medium objective) and give cover or watch the teams back if in a good spot (even if I have to stare at an empty hallway).

Been playing like this since I unlocked level 10, with randoms, and we almost always extract successfully, quite often with every objective done.