High Elves vs Nurgle

So I'm trying to paint the map. I made the mistake to declare war on an human race ( don't remember the name of the faction ) early in my campaign and then crisis happened and suddenly I'm in war with all of the good side guys like +10 different factions. It took blood , sweat and tears to beat the humans and dwarfs but I finally did it. Now I have half of the map conquered and the only enemies left are 2 factions of nurgle and chaos dwarfs. I declared war and ofcourse again its me against all the rest. I carefully prepared for this so I have 60 full armies ready to fight nurgle. First I thought this would be an easy steamroll since they don't have steamtanks , ranged units or artillery like the empire and dwarfs. But after my first turn they attacked my legebdary lord arriele and she just got obliterated. I had like 8 melee units and the 10 sisters of averlorn. Nurgle just walked trough my melee frontline and caught my archers in melee. And I lost the battle. So any tips what units to build or how to counter nurgle ? I still have 59 armies left but their balance of power is almost equal as me and since they defeated my LL so easily i'm scared to lose my 250 turn campaign 😅.