Damage isnt an issue untill 32/33. With madstone you can pop up to 4 decoys from a single sss.
That's more than likely a bug that'll get fixed.
They already fixed the bug were fulminating onslaught was spreading EP to all mobs by the AOE which in turn in with a lot of mobs you could spread EP and spawn a lot more clones. Im positiv its working as intended atm and not a bug at all.
Madstone's EP proc'ing Monkey King bonus, no way that's intended when those EPs don't cost any spirit.