Erebus is fine now. That perma Mist form never worked against my team and I mean never, not even on Exile. All you have to do is make sure Erebus minions are dead when your wave of creeps goes through. The perfect job for a TB.
Im talking about an Erebus who can just swarm > bite > mist then come out and repeat. If he gets on low hp he can just stay in mist and wait till swarm comes back or help arrives.
If Erebus is going directly into mist after he bites, the debuffs from bite aren't worth much, now are they? In order to get the most out of bite, Erebus has to time his attacks very carefully, to include managing healing so that he enters combat at something below optimal health. It's not that easy to do. While I agree with you that Erebus in the hands of a skillful player is still one of the more powerful demigods in the game, a further nerf at this point is just ridiculous. I have mixed feelings on the HoL exploit. Part of me thinks that it should be removed for both Mist and Shield, and part of me thinks it should stay. Either way, it's not a particularly big deal.
As far as the Rook is concerned, his OP-ness is extremely map and opponent specific. On a map with limited avenues of manuever and lots of chokepoints (Crucible, Exile and kinda sorta Cataract) against opponents that are crap at attacking structures, you can have problems, but even then every single demigod has the ability to attack structures efficiently, either through skills or minions in the case of generals. Rook and QoT using intelligent teamwork on Crucible is basically the most extreme case imaginable, and even then they're going to be hard pressed to deal with an Erebus that can jump across and retain flag control (QoT is at a disadvantage solo vs. a good Erebus and Rook cannot leave his farm to recap in this situation), a Regulus or TB taking on the farm, UB spitting, Oak's minions, etc. Sedna, because of how crappy Yetis are, is the only DG who really has little to say vs. a Rook and his tower farm, but even she can be very effective in support of an allied DG with Heal, Silence and moving in for a Pounce burst when Rook gets low on HP.
As much as I find Rook frustrating at times, I would rather not see him get nerfed. He has significant downsides to go along with his advantages.