I've got Stone and Iron..... I mean Balancing suggestions to suggest for Angmar.
Durmarth's level 3 ability (can't remember the name, the one that give Armor to a Hero) seems rather weak. It is very useful for earlier on in the game, but it really loses its flare later in the game compared to other heroes that can give Invulerability to multiple heroes at once, such as Thorin Oakenshield and Beregond. This is somewhat counter by the very small cooldown time of the ability, but I don't think that it is enough. I think the improvements to the ability should be stronger then they are now. Also, it's is a hard ability to put off because Durmarth has to bright next to the Hero he wants to use it on, and it takes about 5 seconds for the animation to complete, which is risky to do while in combat.
Zafragor has too much Armor. I know that his increased Armor is what counters his abilities hurting himself, but it is so hard to kill him, even with Hero Killers. This is the main reason why, in my opinion, he out preforms the Witch King in combat.