I would be very focused on slowing down his unit production early game. A DH and archers might not fight well vs. Foots and an AM like you stated, however I know miltia can't take a DH and archers constantly harassing him.
I haven't played vs. this strat in awhile, it is pretty hard to counter and I would probably lose to it now because I haven't practiced against it in a long time. However I believe constant harassing and slowing his unit production while you tech or mass or put up a tower or something to protect you is the key.
Look for good jacks early game, keep the AM's mana as low as possible and detonate wisps on the AM/Elementals when he hits you with mass units.