Note: I haven't got to the tower of despair yet. I'm waiting for my whole team to level up to level 50 (like on my 3ds version) and then beat the tower of dread and despair on the switch. I've only beaten the 3ds tower of dread.
So, I just wanted to share how I beat the tower of dread. And maybe it could work with despair too, idk.
I have a full party of level 50's and legendary gear. (A mage, scientist, cleric, and princess.) And we beat the tower of dread.
So, I didn't have any vampires in our party (i know it's pretty stupid :/).
BUT, I went to the traveler's hub, and luckily, a vampire mii was there! I also made sure that they were a temporary ally and not just one where you have to defeat a monster for them. So I took them with me and went to the tower of dread.
For the first 4 monsters, I just used my attack move to save MP and sprinkles. after the frog king and frog queen, this was when i started to use my magic attacks.
It really helps if you snag a mii from the traveler's hub, especially a vampire mii if you don't have one already. So you've got 5 other allies helping you. (the traveler hub mii and the horse.)