The Ancient Dead require completely different tactics to fighting bandits, orcs, and goblins. While Ancient Legionnaires function very much like Orc Warriors, the armor requirement to effectively fight them is not nearly as high because their swords are basically weaker Arming Swords (that don’t cause bleed, unlike basically all bladed Orc weapons). Other thing is that Legionnaire shields are reasonably breakable for Axe specialists, unlike Warrior shields which are a waste of time to try to break.
They do a lot more damage than orcs when you consider their ability to focus fire with multiple deep lines (and the fact that unlike the random flailing of orcs, they make damned good use of that ability). They also have higher defenses than orcs, and if you break their shields the damage they deal out individually starts to be competitive (while ignoring the fact that much of their damage will still be coming from the back line.)
Agreed that they can Focus Fire a single guy. You work around that by using a typical staggered formation, where the Brothers with the best defense (i.e. using Heaters in this case) form the points of the formation, and sponge the pike attacks, where as the rest of the line chew up the Legionnaires that inevitably will try enter the gaps in the formation. Use Rotation to swap out the guys on the points if they’re getting unlucky on the hits.
Orcs instead (Warriors primarily) will get to your archers one way or another by knocking your wall out of the way, and chop up your archers before you get through their 400 armor.