Gravemaker I think is dubious to pidgeon hole as a tank and the reason he is such an effective tank is his DoT. If you neglect his DoT it will do less damage as players increase thier defense. Making gravemaker less then ideal as a tank.
In other words I think it’s a double edged sword if you go all defense you neglect his damage and he still becomes a worse tank.
If you go balanced he might be an ok tank but never to his max potential.
If you go all atk he becomes significantly stronger on atk his tile damage goes up his special damage goes up and his talent goes up. He might not be the best tank anymore but he will always be a great flank and/or wing.
My suggestion go atk and find a better tank. Kuchen, guin, ares, Delilah, Santa or the new awesome tanks in khiona and inari. Seriously rogue tanks are a pain. Forcing players to rely on tile damage only charges those tanks up faster. Or they can try thier luck with special damage and have a 1/3 chance to do no damage. You can’t even silence talents as it’s innate. It makes rogues very durable.