Honestly. What I am doing is DUOing the "CRAB" BAMs in the Hatchery (Location: Outside Frontera in Arachnea)
Go to the 3rd floor. And kill these BAMs. Level 45-46.
They drop excessive "Archrune of Titans" 4-7 a kill if you are on a good streak. (They also drop a good amount of Arunic Panacea)
On my server, EVERYONE NEEDS these runes, they sell for 7-10g depending on who is undercutting who.
Best day so far we farmed for 5.5 hours and sold ALL 3200 Runes @ 8g ea. Netting us 25,600.
Right now I have 37k gold.
Hope this helps you guys!
EDIT: Fixed numbers