Ap or Altap

Jumping demons are much better because they can quickly reach and attack. And they have a chance to retaliate, as well as summoned stacks.
They don't get halved because their resilience increases.

I agree with you to some extent... but their target is archers and mages; they lose to regular infantry...

Get artifacts that boost speed and initiative... and you'll compensate for the fire demons' weaknesses.
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*no one is perfect...