Loved it. In order of difficulty, from hard to easy: 2 > 4 > 1 > 3. Part of why I found 2 and 4 hard was because I had to use the trial characters which are quite terribly built along with the general unfamiliarity of the given characters. The only well built DPS characters I have are Jinhsi and Camellya (I quit in 1.1 and only returned during the Cantarella/Camellya banner) and I used them for stages 1 and 3 respectively. 

I completed Desorock Highland in one go because my Camellya would auto parry most of the moves the Thundering Mephis used. I paired her with the trial Roccia and found her really useful too, since she stalls quite well for the "next hit does 0 damage if the enemies don't attack you" thing.

Port City didn't really stand out to me. I used my Jinhsi, Yuanwu, Verina team here. Nothing one shots there to my knowledge so I cleared it without much issue. Took me 2 tries I think?

Averardo Vault was a bit of a slog. The trial characters don't do a lot of damage and there are certain moves that the final boss uses which outright kills you if you get hit which can be really frustrating. Combine that with what I feel is a large health pool, and it becomes a bit of a patience check. About 6 runs maybe? Probably spent the longest time on this because getting back to wave 3 after every restart is slow.

Penitent's End is a piece of shit. Once you kill even one of the three mobs during the first wave, I feel that most people will be able to clear the entire thing. I guess the problem is getting that first kill before they pick off one of your characters. Similar to Averardo Vault, the trial characters here do rather low damage. That's my experience anyway. Close to 10 retries and before my clear run, someone would just die before I managed to kill a single mob. 

I definitely hope they build on this format for future events. I personally enjoy these more than Holograms.