After thinking about it, I think I want to Lead From The Front. We have useful insights and bonuses that Kazador, for all his Thunderhorn prowess, cannot replicate -- our knowledge of skaven tactics should at the very least help out narratively, even if numberswise he still beats us. Fighting alone, we can cause devastation, but as part of a spearpoint with an army behind us, we can open the door for a complete dominance of the enemy. Substance of Shadow+Smoke&Mirrors->Universal Confusion+Smoke&Mirrors back will let Azul's crossbows just dunk all over the skaven forces, and with Branalhune we can help Kazador double-team any skaven heroes that show up. We're the invading force, which means that the fight is wherever our army is, and so that's where we want to be helping the most.
Also, we're gonna get a shitload of Dwarf Favour. Leading From The Front is, like, their thing.