It all depends on what you want to do with your time. I just dropped herbalism on my warrior and took up blacksmithing (I already had 375/375 mining). Why? Because I want to go weaponsmith when I get high enough level so I can make one of those awesome tanking weapons like Fireguard. My guild's not going to see anything higher than Shadow Labs for quite a while, so I'm not likely to get anything better through drops (unless I pug, and on my server, that's akin to madness). So since I can already farm the mats I need between my warrior and other alts, it was a no-brainer for me. I actually enjoy leveling the skill up, but it does take some money to do.
However, if you're in a guild that has no trouble with the instances, and does them quite often, you may want to stick with skinning, as you'd get most of your gear there. It's pretty much up to you and how you play the game.