I did a lot of test
I will suggest story 2-2-8 (the royal bloodline)
1)8 enemies (any enemy has roughly 85%-90% of drop a chest)
2)Any chest has roughly 20% of cointain a faint memory
3)energy efficient cz u get 1,4 memory/6 rng
Ps u need mediena one shot one row of 4 enemies and a friend mediena to one shot the other row of 4 enemies
I noticed this stage when I was farming for some crafting materials. Usually I get 6+ chests every run. Not to mention other "more than 6" enemies maps give me only 2-3 chests. Thanks for sharing this!
idk if this is considered efficient, in a sense that you will be paying attention most of the time yes, but in terms of auto repeat and letting it run, not so much