Treasure Hunt can give you a decent reward if you do it right.
Today I got 15myth from a peisteskin map in a 2 minutes fight.
Now, if you build a Treasure Hunt Party and, either gather maps(1 every 18 hours) or buy them(, you can optimize the myths.
Lets say all of your members have a map, and each map will give you 15myth,
in a full party, with 2-3 minute fight you will be able to get 15*8=120myth in 20 minutes average, plus gear, gil (5k * 8=40k), and even crafting/housing materials.