I have been unable to confederate Orion as the Heralds of Ariel. When I complete his confederation quest (sack/raze 10 settlements) it completes the quest but no prompt pops up to take the confederation choice. I do not currently have a confederation penalty for confederating other WE factions. I have tried it while Orion is wounded and when he is unwounded. I have already confederated all the other Oak of Ages WE factions.