@xxPrincessLunaxx, you can ealely defeat him with maxed stuff and an elixir if you fight him early enough. You'd probably need to have used a voucher to get your HP/Atk on par, though.
@wolfbanes, the 4 star thing gets easier once you manage to filter out all except one type of costumer. That way, you can accomodate all rooms to their needs.