Transmute mastery is a pretty long-term investment. You'll have to do a lot of transmute to pay for the initial cost (primal mights). That being said, I usually think a tradeskill is worth it if you use the items you can make, and potions are nice to have when doing the later instances (especially heroics).

On my first team I had jewelcrafting, skinning, herbalism, mining, tailoring and alchemy. Mostly I used the herbalism to make potions and sold those I didn't need (occasionally I sold the herbs since they would sometimes bring in more than the potions). Leather I just sold on AH, but I think it's more profitable to use LW to turn them into greens/blues and DE them. Same goes for tailoring - use your looted cloth to make greens, DE and sell the mats.