Leveling cooking is not a waste of time.  Leveling cooking by buying ingredients is, at least in the low to mid level range.  Just level it as you go.  Whenever I'm in town and in the mood I go cook whatever I have.  Most times cooked items sell for more than their ingredients.  Also, I save the ones that give a buff.  It's not a skill I actively seek to max out normally, but rather over time I inch it up.  At higher levels it usually pays to process materials into finished products, so why not have the ability?  Just download one of the add ons that helps you manage it, and you can queue up things so you don't have to figure out the best stuff to cook all the time.