Got some news in. Grukk got the following profile (everything is standard like a normal warboss except for:)
He costs as much as 13 Ratlings.
His Klaw got the shred special rule. And he comes standard with Feel no pain.
He got one of the Warlord traits in the Ork Codex, the one that let you reroll failed moral checks.
And all the sprues are the same as in the standard boxes you can buy. With all options.