actually, no, the tactic for Necropolis is exactly like that! You take money, buy everything, and turn it all into skeletons! You say that too many skeletons won't save you, and that vampires can be quickly defeated! In my opinion, this is one of the most difficult tasks, IMHO... I remember playing too... with Ulan, I think - he also thought that vampires were nothing, and he was slowly defeating them... but in the end, I wiped out his entire remaining army with them!!!
P.S. If you "slowly defeat" the vampires, then it really is "one of the most difficult tasks", but if you act intelligently, it's quite easy ;)