I doubt this is possible to do, but I’ll put it out there anyway.
I’m guessing by now there are a lot of players with level 99 arkadions, so when the online missions come up it just becomes a case of who’s fastest to get through the dungeon quests to win the prize, unless there are battles where you have to use a particular strategy. I don’t find the dungeon quests particularly interesting either.
How about something like a treasure hunt using the actual island i.e. you give out clues, you have to find the location and win a battle for the next clue, until you get the gold egg. Something like that seems a bit more interesting; it wouldn’t be a mad rush to whoever is lucky enough to reach the top floor the quickest and incorporates a bit of skill and can also still put in tougher battles if the clues are easy.