My experience within 15 generated assaults is power projection in one defensible area then lure the enemies to that said area. Camping as they call it, three decently survivable well positioned tanks with a lot of firepoweris enough.
The AI usually keeps pushing my position in a sub-optimal manner with limited force, even with heaviest of tanks are too easily eliminated. I had encounters with competent AIs that knows how take cover reveal mostly their thickest armor but they still are usually outgunned to be a threat. Flanking is a threat but it's rare with minimized effect thanks to the sensors.
I suggest adding threats with indirect strikes and better AI.