While I agree that Harbinger is a very good caster there's a few things I want to point out to you that I feel might have been overlooked.
Her control range is huge... But her ability Awe is command range (10") not control range. Add to that that it only affects living models and your defenders and hunters (yes armour piercing will work agains her) should have not that much trouble hitting her. That large base is one of her biggest weaknesses in that it's nearly impossible to screen.
Another tactic when he's forcing you to play the ranged game is hitting his key solos like the vassal (if you can get to him), Vilmon and any other solo he speaks fondly of. Hammer them and force him to Martyrdom, hopefully getting him down quite a bit.
Having a way to strip that focus or forcing him to spend focus on Purification and Cataclysm are a good way to lower his defences. As I see it he's spending focus on his Vanquishers... Purification is 3 and Cataclysm is 4. Even if it costs you the Black 13th and for instance a Blur upkeep , you'll be ahead of the game when you can line up a shot on him next turn with your defenders and hunters.
She dies to a stiff breeze when low on focus. Also get eEiryss (I know pEiryss might be more effective against some lists, but eEiryss is just more versatile in general), if he wants to get down and dirty it's time to even the odds.
Download Steamroller 2012 and play scenarios. Nothing is worse then playing a non-scenario game against a gunline.
Good luck!