[Taqwus]

I think that, versus undead, I'd want to have something like Mechanical Men, Living Statues, etc up front -- something with good prot that won't rout or fatigue. The latter is useful due to the large numbers possible, while the former helps due to the not uncommon fear effects (Behemoths and Wailing Ladies cause fear; the latter is likely to be especially strong as they're unholy, and Dead Ermor is likely to pick at least four points of death...). In addition, I have far fewer qualms about risking friendly fire via flaming arrows when it's only constructs in my line instead of potentially expensive heavy infantry that I might not be able to replace very quickly or nearby.
If it's against Soul Gate, your front line is also risks paralysis and disease, and will need to swing more times to hit ethereal units barring something like a fire-9 blessing (or Weapons of Sharpness? Need to check. Caelian ice weapons also count as magic, ouch.)