Help me survive against Ermor

[General Tacticus]

Longbows not working ? Are you using enough ?

Actually, if you are going for a war of attrition, you need to find yourself some very cheap cannon fodder, and put it right on the front line (anything that costs 3 or less resources and less than 10 gold will do). That way, your expensive heavy infantry (on hold and attack) will be able to break the enemy without great losses, and hopefully your priests will have dealt with the undead before that.
Plus, do your best to encircle the enemy to destroy him when he does rout.

I must warn you, however, that Ermor, even Broken Ermor, is not the best opponent for a war of attrition. And I a not sure Man is the best nation to try it either

Remember, for a war of attrition, you need to kill him faster than he can recruit, while taking losses no faster than you can replace them. Losing expensive units, particularly one with high ressource cost, is not the way to do it.