the fact that he willingly transferred the guild is going to keep you guys from getting the hours back unless Xor makes an exception like never before
guilds like Total Inception and Munchies were also stolen this way, it's just that the hours weren't reset

pretty sure your only shot at getting the guild back with its hours is if Diablo is able to come up with an excuse to claim that the hours were reset by an admin through some misunderstanding or by complete mistake, and then he willingly hands you the guild back