Not so hard to master, just don't forget to mix-and-match your 'goddesses' weapon and elemental types. Always check the enemy spawn range on the mission's briefing. The only hindering to progress are materials needed for lvling and enemies' battle power.
Some of the characters are subtly censored, kinda dissapointed tho.
And mark my word, someday Chinese devs out there will plagiarize this type of gameplay mercilessly.