Battalion + Spearhead + Outrider + Battleforged =8.
-3 For 2 Extra Artifacts - 1 for Alliance of Agony.
So 4Cp is correct, my only issue is you can't have both of your archons have warlord traits, plus who is the second HQ in the battalion.
Alliance of Agony gives you 1 trait to a succubus, and 1 to haemonculus, but none to an extra archon.
I put this army into Battlescribe, and i have it at 2077, i think you simply missed the 2nd HQ choice for the battalion, which can be remedied by removing the Sslyths (i have all court of the archon units, over costed with little benefit).