How to farm Divine Dew??

You only get Divine Dew by using refining stones (excluding quests and map rewards).

If you're running low on Stones, then, if I recall, Arena gives some. I think Arena Assault does too? There's usually quite a few quests and maps that give Stones as a reward.

I personally don't use them all that often. Majority of the units I use on a daily basis either only needed the one upgrade via stones or don't have a refinement.

But if you're really need of them, make sure you do AA every week(Sounds like you do), make sure you get the reward for RD, and lastly just upgrade your 5* weapons for units that need them. If you're going to run AA, may as well have a lot of units built.

I guess your Divine Dew output is directly proportional to the amount of Refine Stones you get.

I guess just focus on building a core team for Arena Assault full of +10 units to make sure you get the higher tiers of rewards?

Divine Dew is very limited. I would say it takes about a month to generate 200 Dew to refine a prf. Think carefully about which weapons you want to refine. I have some regrets that I wish I could have the dew back for.

If you are only getting 14 stones today, you aren't doing the best in AA. Are you starting it with a merged team? Does this team have high SP skills? Is your run deathless? Are you using 7 teams of all proper seasonally blessed heroes?

Seems you may need to adjust if you aren't meeting those conditions. I normally get about 19, which then 5 stones don't sound like a lot, but add that up over weeks and that's additional refinements.

If you don't have a good merged team, then that should become a focus. Determine which units you have many copies of, and make some 5*+10 merges. Or pick favorites. Make sure Alfonse, Sharena and Anna are 5*. Feathers are farmable if you are willing to put in the effort. This is accomplished with HM farming using Rival Domains.

If you havent done blessed garden you can do those for 20 dew per missions, you need 4 heroes with the same blessing as the garden to enter.