[Boron]

The black servant is so-so. He is good at raiding other players. Full gear is not worth it imho, but if you simply give him a shield + an armor he is already quite ok and costs not that much. But he can only be used as a raider.

Vs. real enemy armies he is way way too fragile. Since he is undead and has low hp, it is not worth it to invest too much into him.
A tartarian can survive a few dust to dust or lightning bolts etc., a black servant does not.

But by being available so early in the game he is a perfect raider. Unless your enemy is lucky and has priests or a useful mage as pd the black servant can easily beat pd.

It is not so easy to defend vs. them when they are raiding. you would need to detach 1-2 mages or some priests to every important province to stop them reliable.
You can do this, but if you do this your enemy has already achieved an important goal: to severly slow you down.
Imho the black servant is fine as he currently is.