I chose 2.4-9N ( see notes ) because the recruits are better ( 13, 15, 16 ) versus 2.4-3N ( 10, 12, 13 ) or roughly 25.71% more recruits.
Dragon Bones
2.9-4N is recruits ( 16, 18, 19 ) and 3 mob waves ( ( 3, 5 mobs ) x 3 waves ) and 1 Boss +2 mobs
So better at 20.45% more recruits and 50% more monster than
2.9-10N is recruits ( 13, 15, 16 ) and 2 mob waves ( ( 3, 4 mobs ) x 2 waves ) and 1 Boss + 2 mobs.
Meteor Fragments and Orichalcum Nuggets
I thought 3* / 4* items had double drop rates in normal and triple drop rates in hard by taking away from other 3* / 4* items. So if you only want Dragon Bones, then 2.9-4N is good.
But if you also want Meteor Fragments and Orichalcum Nuggets Season 2 Province 7 ( still 15 crafting ingredient loot rolls, increased chance of Fine Steel but same chance of Dragon, Meteor and Orichalcum ) might be better ( see note on crafting ingredient rolls per energy ).
Coin
Has anyone confirmed this for coins?
See @zephyr1 discussion with Devs in the notes below.
Notes
Click for notes
Rugged Clothes
Atlantis Coins
Crafting ingredient loot rolls
This becomes 15 per 3 WE for 2.7, 2.8 and 2.9 during Atlantis Rising compared to 13 per 3 WE for 2.6-9N.
