Is Conflux a broken castle?

At first glance, Conflux doesn't seem like an overpowered Castle, but I once played against a Dungeon Conflux and got completely crushed. Then I tried to counter it with a Castle, but even the humans didn't stand a chance. Overall, I've come to the conclusion that Conflux is a really powerful Castle and needs to be taken out before Phoenixes are built, otherwise the opportunity is lost!