Just pick up a few idol minions as sedna and that will level you up plenty fast enough. Just being around creeps that are dying gives you plenty of experience. You only have to do the damage if you want the extra gold.
As regulus, he can clear out creeps either with mines or with angelic fury. What other skills could you possibly use if you don't use one of those two?
Unless this item took 2-3 minutes to recharge it would bring too much concentrated extra firepower to early fights. Like Daikaze said, you'd be able to nearly instantly bring down 1 lvl demigod to half hp or much less.
If this item only affected creeps then maybe it wouldn't be so bad. But Heavan's Wrath is just as good as this item would be. It auto-kills priests and below and deals enough damage to catapults that you get gold and experience from them too.