One question is, the character Maul doesn't appear in the orc camp.
He doesn't appear in the orc camp of the battle grounds near where the city is. He appears after the orc war(siding with Korg).
The orc camp you need to be in is much more above the map, you'll see a cave directing up there. (It's a long journey to continue this).
Once you managed to finish some tests given up there, you'll be able to walk around and enter the battlegrounds there, he'll appear with a dialogue wrestling over other orcs in that camp.