I disagree that Necropolis is weaker than Stronghold. By the second or third week, with Lords and plenty of unit-boosting objects, they even surpass them in tempo.

Well, I was focusing on the first week, because generally you can hardly do anything — you try not to lose what you have, rather than building up bones, even with Isra and the boost. In the second week, with Lords, if you have something to take with them, you can catch up in tempo, but what can you take with Lords? Griffin Conservatories, Dragon Fly Hives, Crypts — Crypts are questionable, Pre-Maxes and Maxes are dangerous, one proc of morale and that's it. Any other town can also easily clear all the aforementioned objects without major issues, except maybe the Max Griffin Conservatory, but even there Lords can have problems if the hero isn't sufficiently leveled or if a few unlucky morale procs occur.