Well, that's not an argument; you could summon VD as well.
Why isn't it an argument... It's just that when choosing between who to build and who to summon, I choose: build CD, summon Phoenixes. To my taste...
I understand you know a lot about them. Are they really such !!!!! , that no one is a threat to them except CD and heroes with magic protection?
Could you please suggest how other castles can fight them?
VD is simply good in many ways. I highly value variety in actions. You'll agree Phoenixes don't have that... Fly in, bite, be reborn... How to fight them? It's always hard for me... Stealing energy (so that spells cost them more) doesn't work. Magic protection will definitely help the hero, and the army too. Therefore, the solution is to look for a magic protection artifact.