Ordo is significantly above Kisui. It's also fairly logical to assume he has some commanders with as much muscle as Batei, if not more so. He has an army that is perfectly used to climbing up hills and fortresses as well. Kisui isn't going to be able to psychologically crush Ordo which means it will be a physical battle. Even the Ousen army didn't want to mess with Ordo in a direct confrontation. We've seen enough of tribesman to know how this goes down.
He lost to Ousen who could sike him out, and was later stopped by 5k Shibashou + subs whilst Chouhaku attacked Yan to essentially force Ordo's hand. Kisui or his army aren't capable of that level of warfare. Remember Kisui was completely taken apart by Ousen's day 1 move at Shukai Plains - he'd get destroyed even more than Ordo if he ever went one on one.
Kisui would up up a good defence because he himself is strong and the Rigan army is a powerful force in defensive situations, but it's underestimating Ordo to think he'd lose here.
