It’s moves are SOLO 
Otherwise, great post.
This is a guide I should really go back and finish off properly (or make a dedicated one for each event). Whale’s Treasure is at the bottom where it gives a bunch of useful tips including some thoughts on the rewards:
KD’s How to beat each event (+videos)
For the boss battles it’s possible to build specific teams for beating them, sometimes using monsters of a different element. For example, Aurodragon + death revenge or sleep lock or sleep + 400s novablast. For the standard battles I’d recommend just going with the best monsters you have for it and letting good friend monsters help you out.
As for the best friend monsters, there’s a lot which get the job done for the standard battles. Sometimes you get a nasty enemy team, but typically what you want to do is leave the enemies that aren’t buffed then tank you way through their attacks as you clear them out with stuff that’s hard to face. For example, Doomgoo does well in the fire area. Charybdia does well in the water area. Think tanking, piercing, cloning and stuff like that.