Even in virtus ("max" ancients gear) you still lose damage as a whole because:
a.) you are wearing a slayer helmet, not the Virtus mask, so you "miss out" on the %magic damage the mask has,
b.) you are now "required" to pray Augury to get comparable dps to before, even if you are attacking something with zero magic defense like a Dust devil. %magic damage on Augury is not a bad idea and is good long-term, but this change for the same dps we currently have without acknowledging it as a nerf across the board has to be acknowledged, especially because this example has the player in best-in-slot gear. This could be mitigated by %magic damage (lesser, like 2%) on Mystic Might, but is still an issue that needs to be acknowledged.