I achieve Platinum III today and more difficult teams appear than in Platinum I or II. For example, I have found many opponents with double or triple tanks and Pomona or Neptune .. or with Rita and Bathory, or the new Sytry.
I'm not so sure I can go beyond this category, for now it's not bad but I think in order to be able to move forward I will need to create a different team. The team I was thinking about is one with Sytry, Limos, Bathory (Leader), Neptune and Chang'e. I don't know if it will be a good team, but I'd like to test it ... but both Sytry and Limos do not yet have uncaps or skills up, so for now is not possible. An alternative would be to use Salome instead of Limos, his poison targeting three enemies is really interesting. Good luck with your Devil Runble.