I also take Adepts; they are overpowered:
They have +4 attack, and with equal hero attack and defense parameters, this is a +20% damage multiplier.
+They cast Bloodlust at the expert level, which gives +12 attack, meaning +60% damage to the selected unit.
And on top of all that, they have the Purification passive skill. It's always nice to remove buffs from the enemy.
Incas are less effective, even though they have a much larger set of buffs.
Well... It depends on how much game time you want to consider. In the "early" battles, within 1-2 months, you won't have enough Adepts to realize their offensive potential. Monks are still more of a tier 5 support unit. Plus, you can turn them into cavalry.
What's this Bloodlust? Karaka?
However, maybe I was underestimating the Adepts. It has happened with units before.