Mordor Catapults in Battle for middle earth 2 question?

I play BFME with a bunch of friends and its really fun until this dude came along and started playing with Mordor. His Nazgruls would rape everyone's base before our armies even met. Playing with the elves, I easily killed his Nazgruls with Mirkwood archers. After a few turns of sweet victory, he started creating an army of catapults that raped my archers before they could finish him off. Eventhough I tried different tactics with a mix of cavalry and archers, nothing seemed to work. Any advice?