The last map of the operation, with a decently difficult boss for newer players or players not used to micro. You'll want to have two combat echelons for this, and ideally three dummy echelons. You can easily do it with two dummies, but I feel like it's best to do with three. Do note the echelon defending your base can be weaker, since you easily can quick repair there. 

This is where the difficulty starts getting increased. You'll definitely want to use two echelons here, as well as a dummy echelon. This is also the first map that can drop Noel. Farming this map, in my opinion, would be a better option than farming the last map. As she's a reward for 99 Seithr box openings, you really only need to grind for her if you want multiple copies. 

It's recommended that you pack a second echelon for this map. Otherwise it's just a slight step up from map 1's difficulty.

So, Operation Rabbit Hunt is here, our first collab event. It's not a particularly hard event, most collabs aren't. It's intended for players starting because of the event to finish it, so don't expect this to be complicated like some of the major operations. I'd place the difficulty of the enemies and such to be at around Chapter 4 or 5's level. Going in with an echelon at around that power may prove to be a little difficult with the last map's boss, but it's very doable, especially if you use quick repairs.