They're actually not overpowered and here's why:

1. They have no defense at ALL
2. They have virtually no way to escape enemies when being pursued
3. If their Aetherflow stacks aren't available, they're pretty weak as their main damage component comes from their Aetherflow

So, if they didn't have these three major weaknesses, then I would agree their OP. But, that's not the case.