I don't know ? Are you flanking or going face to face ? Theres no real answer to this type of question. Hammer beats High armor, Improved Armor Falx better than Rhomphaia when going face to face without flanking. If you can manage to surprise the ennemies in the back with Rhomphaia i suppose it will massacre them, i see it as a "glass cannon" build, you must be tedious while playing it. This right here is, in my opinion, what would be the logical thing, but is it really the case ? Captain tends to show how unbalanced some classes are. For example, Tribal Warriors may look alright on paper for their price and the amount of units it provides, but when they truly engage into a fight, you just see how horrible they really are, they barely make a single kill.
Captain mode, by the end of the day, is like playing a big "rock paper scissor" game, no matter what troops you choose.