You should farm them at dragon forest || and the forest that disappeared. I recommend using an arch mage, it was really fast using my level 120 mage.
i think the burning forest is better than the forst that disappeared. you can stand in the middle of the 3 platforms and farm all 3 platforms with a mage ultimate. pretty sure it's a better map even if you're not a mage. you never have to leave those 3 platforms, the spawn rate is pretty high