Is Conflux a broken castle?

Conflux is a strong castle, but not overpowered.
Fairies die quickly. Encountering Fairies is a dream for a Necromancer.
Strong, unupgraded units of levels 2-3 - how else?
Fire/energy elementals - an average unit considering everything.
Earth elementals - that's just ridiculous.
Psychic/magic units - the damage is area-of-effect, but only 75/80 health and low damage.
Birds and Phoenixes - well, they need to compensate for the weaknesses somehow.
In general, the castle is very dependent on upgrades, although they are cheap, they take resources and time.
University - but don't you want to pay the money? It's not overpowered in any way.