Compare the results of 1-on-1 battles of vampire lords against, for example, minotaurs, 10-on-10, and 100-on-100. Were you impressed by the difference?
Added 4 minutes later
Of course, the real strength of vampire lords was meant, that is, the combination of resilience with all other factors. A large group of vampire lords recovers better than a small one, thus 40 vampire lords are stronger than 4 squads of 10 vampire lords. Naturally, this applies to most situations, but not all.
