Pikemen have no armor. The armor upgrades are not working and half-plate pikemen have less armor than troops with padded (3 vs 4).

I actually have no complaints with pikemen when they work correctly. The first time I used completely unarmored Tercios in open battle they saw off dismounted Norman knights with three silver chevrons. I now use modded Tercios with armor set to approximate what they should be getting (heavy mail = 7, mine are modded to 6) and they work fine. They just bug a whole lot and it's impossible to attack with them.

One thing, take them off guard mode unless expecting the enemy to charge, otherwise they don't fight properly half the time.