I´ve noticed you can really fuck with the vehicle AI when there is a cliff or some other obstacle that the vehicles cant drive over. Had a mission with a couple of those 2x AC 20 tanks and I just played rope-a-dope with them. They were on a cliff above me and one of my mechs was in range to be shot with the AC 20s so they moved towards the edge of the cliff to fire. I then moved that mech in range from the cliff top further away and the tanks started going around the cliff to get to me. Once the tanks had moved once, I moved my mech back where it was and they came trundling back up to the cliff edge as it was in range again. I just kept them moving back and forth like that while I dealt with the actual enemy mechs.
As to the other comment about the end game being stale, I agree. I´ve got full assault mechs, full ++/+++ weapons on them and griding the same 5 skull missions over and over got old real fast. Here´s to hoping the expansion/DLC breathes some life back into what is still one of the best games I´ve played in a while.