Regarding point 2:
It makes sense in late game. It doesn't work well in fast games. There is little mana.
3:
Warrior skeletons are strong in the late game. Very strong. Stunning strike works often enough. They have huge damage. Initiative is also good. Verdict: the main attacking stack;
P.S.: You are straying from the topic, gentlemen. Posts concerning only Necropolis should be written in this section.