Haiden is not a tanky unit, but he has very high damage, making sure you're the one to engage the enemy if you need to get through. You also have access to Leif and Aeren for that mission who are tankier units if you need to aggro enemies
I managed to do it after a few tries but the enemy positioning was a bit rough lol. BTW are the Feeble Clothes implemented? I have Asker and Haiden's and I checked the little box for them before the battle on my units screen but the boys taking damage doesn't change the outfit
