Yeah the main problem with White Lions in my experience is that they just aren't worth it in campaign, they will never be a frontline unit unless you're willing to give them a lot more durability. As a flanking killing unit they still suck ass, because you haven't touched their shitty movement speed, or given them a significant enough melee boost. The armor sundering is a good idea, but definitely buff their movement speed, and maybe throw some extra HP their way, with anti-large and armor sundering they'll be good at catching heavy cav... except they wont because they're too slow. Maybe you could drop the anti-large and switch it with anti-infantry? and maybe throw 2 or even 4 extra weap strength? Or keep the anti-large and buff their movement speed and HP and throw 2-4 extra weap strength. That way they can have a bit more durability, and more potential to cut up heavy cav and armoured monsters, and even potentially armoured infantry.

this is lame...they are still trash