Pikes and billhoks have 50% penalty against undead
I am fairly certain it is just pikes and billhooks have 100% dmg. Their damage type should be slashing, maybe blunt.
@Phalanthir I think hruza summarized it pretty well. I would just add a few things.
Since they use a very tight line formation, you can basically tank 2 shieldionaires + 2 pikers with just one shield bro if you leave a hex space between them. This allows you to send more people around the flanks to take care of the pikers. Try to get 2-3 guys with mace mastery to fight them. When they are in a good position, they can keep 2 pikers in stun-lock which will give you time to take care of them and pretty much eliminate the threat. Their frontliners will mostly use shieldwall and only attack once. If your own shield bros will spam shieldwall and sometimes use recover it should be easy to tank them.
You say Archers are useless? Have you ever used warbows before? With a basic one you probably need 3 arrows to completely melt a piker’s armor, leaving them to be a oneshot to pretty much anything. This works especially well with greatswords’ split skill.
Yes, legionaires are pretty dangerous in the early to midgame when your guys are still wearing light armor and don’t have a lot of melee skill/defense. Once you get your frontliners with battle forged and 200+/200+ armors they become much less of a threat. This should be around lv7-8 of your brothers. They will probably have around ~20 base melee defense by then which gets to around 60 with a heater shield and shieldwall, 10% extra from confident maybe.
With underdog to counter surround-bonus and an estimated ~60-70 melee skill on legionaires this will leave them to hit maybe 10-20% of their attempted attacks. Steel Brow also helps mitigate a lot of the damage you take from piker’s headshots (armor penetration)