I use Alchemy + Engineering for the Alchemist Flask and Frag Belt Once you have made the flask and frag belt, you only need classic Alchemy(1) and Northrend Engineering(1) to continue to use them. So you can temporarily drop them for other professions (to enchant a new weapon for example)
Until a possible Professions rebalance in 10.1 we are stuck with pretty much Classic Alch 300 for the level 1 req flask. Northrend Engin 5 or 30 for frag belt at 5 and nitro boots at 30