Honsetly imo this campaign isnt that hard if you can tell what can be your big issue and what not, i think you dont need to attack Malagor or Skarbrand in particular.

I play on Legendary/very hard and what i do is that i capture Karak Azgal turn 1 and then i instantly attack Queek as he is big trouble, on turn 1 or 2 you should be avaiable to get temporaly peace with the Greenskin tribe so you can finish Queek, after that when the Greenskins are set, they will fight you again, but you should be prepared for it.

After wards a Skaven faction may declare war on you (Ekrund Skaven), those guys should be ez to kill if you go mass chav and overwhelm their ranged, then you can make it harder and go and capture their territory, and then you could make it eazier by selling those settlements to Ironclaw for Non-aggresion, bcs at that time Imrik will come and he will want to beat your ass.

I just run away to Miragliano using the cult there to teleport lmao