My opinion on the matchup between Stronghold and Necromancer:
EARLY GAME - 10% advantage for Necropolis (Kaspar, tent, raising undead)
MID GAME - 50/50, slight advantage for a friendly game (depends a lot on neutral creatures and artifacts)
LATE GAME (with a mentor) - 40/60 advantage for Necropolis (the Cry skill is very effective with Deidre)
LATE GAME (without a mentor) - 30/70 advantage for Necropolis (it's clear here - they have more meat, and Stronghold has little chance to develop properly).