I think the nerf was minor at best, I'm not sure it will stop him from being the clearly best demigod in the game right now. I don't think it was the mana cost nor damage that was the problem. It was the slow and massive armor reduc. The slow really has to go. He shouldn't be able to go invul whenever he wants, have a stun to disrupt your chance to tp out, have a blink to get in combat or leave combat, and have a slow/armor reduc/dmg/heal move all rolled into one. This isn't even including his free minions or high base movement speed. A good erub you basically have to stay miles away from or he will eat you.
Suggestions:
Put dmg and mana cost back on bite, take slow off completely, leave new armor changes (even tho they are still high imo), up recharge time slightly.
Up mana cost of mist or make abilities not recharge while in mist.
Up the cast time on the stun? Not sure what can be done to balance this, I'm not sure why anyone would have high base speed, a slow, a armor reducer, a heal, a teleport and a invlunerability button. Most demis can do nothing about the following: Erubus comes out of fog of war, blinks on top of you, bites you, his minions catch up and start wailing on you with your lower armor and movement speed, if you try to tp (stun), if you dont, humps your leg and spams bite, if for some reason you happen to be able to stop him or force him to a situation where he won't win the battle (mist, bat swarm away after cooldown). But that situation is rare once the game gets going.
I see noob erbus's lose for certain, but it seems to me with equally good players no one will beat the erubus.