I have my mage at lvl 46 atm & I have mining & blacksmithing. Thinking about changing them as neither of them are high at all. If I switch to say, enchanting & LW, wouldn't it be harder to level up both of them as I won't get the green's to disenchant from dungeons, and not a ton of linen cloth drops?
First, LW is crap for mages. Tailor/enchanting is much better. Second, if you have a high level you can just send your alt 1000 gold and power level to 300 or so. You should be able to buy enough cloth to make enchanting materials to level. For wool, you will just have to farm it most likely, same thing with rune cloth. Do a dungeon like stockades or just AOE grind some humanoids. Or if you do not have money, just AOE grind mobs. But still, see if your guild has materials or there are some on the AH. Sometimes it is cheaper to buy stuff on AH in terms of time, even at a low level. Once you get to outlands you can start making 16 slot bags and recoup your expenses. Or you can farm some really nice rare enchants for BOAs and recoup your expenses that way, those routinely make 100s of gold since everyone wants to put +4 stats to chest on their BOAs.
Did you mean tailoring? LW uses skinning materials, you'd have to be able to buy them off the AH.
It's not too bad to start enchanting at a higher level. If you are doing another crafting profession, you just disenchant everything you make, and you get plenty of points/materials from that.