The point with Hulk is: We don't want the HulkFlash deck, which had nothing more to do than find Hulk and find Flash, to mutate to "find Entomb" + "find Necromancy/Footsteps of the Goryo", which would cost 2 mana more to perform in a single turn.
We chose to ban Hulk and not Entomb, because Entomb is "broken" with no other card in the format, but can be put to good use in many decks, while Hulk will always be merely a combo piece. Thus banning Entomb would limit deck building far more than the absence of Hulk does. This decision was based on the same argumentation as the banning of Worldgorger Dragon.
I didn't even knew Entomb is unbanned as well in your format, which is a mistake as well in my opinion. The graveyard is a strong ressource in Highlander, even though lots of hate is played in the casual plays I play. But with cards as strong as Entomb, the hate certainly isn't sufficient. I don't know why the decision to ban Entomb should be so hard. And Entomb is broken, because it's simply to good in this format, as are lots of other tutors. For one black, you get a flashback card, Riftstone Portal, a big creature for reanimation, Genesis/Wonder/Anger, Ichorid if you feel the need, something nice to Eternal Witness. And at instant speed, too.