I haven't seen it, yet. I am guessing turrets and sparks will do the trick. When he gets t2 you need t2 as well (probably air or bots start).
Build less air. More turrets. Single turrets will kill a lot of patrolled dox without taking much damage. Protect all your fabbers.
Snipe his fabs, outexpand and outproduce him, skip energy and make lobs, beat him at his own game. or snipe him