[Fantomen]

Consider that such a cost effective defense as this will allow you to stay offensive while being attacked. You can put more of your resources in offensive strategies compared to your opponent since your defence is reusable and needs neither gems or gold.

Say you are playing a strong earth nation like MA agartha. You´d need a blood economy anyway and once your stone factory is rolling I´d say investing in a vampire defence makes a perfect compliment to your offensive armies of statues and mages.