My goodness, sometimes it seems like my regular soldiers came from that XCOM thing. FIRE IN AN ARC OVER THE SHIELD PEOPLE! I'm getting the impression that the enemy has no horses, so just keep circling and such, playing off the speed and maneuvering (and height I guess) advantages, focusing on the enemy archers, they can take out the tower shields at leisure after that.
If the arrows are coming in volleys, charge inward to dodge and then back to the previous range ponce it's over; mix it up after the first time, otherwise, just be smart about dodging and all that.