On 6.2 I have gone through and tried acquiring disciplines for several crafts, here is my feedback:
Alchemy and runecrafting: feel fine. I feel this way because I was able to make potions and tools to acquire the disciplines (something I could put to use.)
Necro: I decided there was not enough time to justify wasting materials on acquiring necromancy disciplines.
Blacksmith: I wanted to focus my time on acquiring blacksmithing disciplines before 6.3 releases in order to make some armor to carry over. My feedback: blacksmithing feels awful. To have to make dozens of pieces of gear that w