Those are some great heroes!
The question about ‘do you have other yellows’ is because if an enemy is purple/dark then yellow/holy does double damage to it, while it’s own color (dark) does half damage. It is often a good practice to build your team to counter the enemy, rather than just aim to outmatch them by strength alone.
I ran into a road block far before you did. I’m currently plugging my way through Province 13… mostly because I’m working on developing a team of 3* heroes before I move on to my new, shiny 4* guys. That said, I’ve had to sit back and not progress for about a week or so myself. What have I done in the meantime? Built up my base, collected ascension materials, and leveled up heroes so I can progress further.
The best way to acquire rare ascension materials is through those wanted chests that pop up so regularly, killing titans, and winning alliance wars… but both Alliance Wars and Titans require that you’re a part of an alliance. Honestly, it’s these wars and titans that form a lot of the focus of more end-game players. They’re pretty core to the E&P experience and will help you through these times of non-progression on Map progress.
To answer the precise question: According to the E&P Data Bible stage 22:7 is 100% purple. All enemies and all bosses are dark. Because of this, you will want to field as close to an all-holy team as possible. Even if they’re unleveled, try out this team and see how well they perform:
Kiril - Wu Kong - Justice - Li Xiu - Chao
It probably won’t win, but if you get a good board, your tile damage will be kinda insane and it’ll definitely show the value of countering your opponent!