So Scarab is about a few things: 1) Team Protection 2) Shields at all times 3) Destroying his Max HP 4) TM control
So Armiger needs to be in, since you've got him in Destroy, he has a Bloodshield ring and he controls TM.
Then I would try and have shields up as much as possible on defensive and protection champs. So Skullcrusher and Ultimate Deathknight are in. (UDK can actually solo this boss without too much trouble when 60d)
After that it's dealer's choice. I might toss in Deliana cause she's got Blooshield and decent damage multipliers, can help us AoE the waves, and is very survivable as an HP champ. Then perhaps Demytha to extend the shields to cover the gaps and ensure we've got even more healing.