There is an easy way to farm that Orichalcum ore and Twilight Bloom Roots in the Instance calles Charmer's Caldera.
All u need is to be a ROGUE.
Just have a look at the screenshots and u will understand how to pass the wall after the first boss.
U can find 1-4 points of ore/bloom each run.
When u are finished with ur run just die reset and reenter, works about 5 times an hour or smth like that.