Yes, the crusading armies are a bit ridiculous, since the dirty crusaders usually have 2 or 3 waves of 2 or 3 full stacks. At least you know they are coming and can prepare some ambushes along the normal routes. Now if they drop them by sea you might not have time to see it coming but trying to sink those fleets is about the easiest way to stop them.

Once caught a mongel jihad full stack in a fleet of 3 ships and was able to sink them, felt pretty good.