Personally i think enchanting + engineering is the way to go for a main character because of the nice engi-only bonuses for PvE like the reflectors (+40 SR for warlock tanks at twins) and the AQ-teleport trinket (real time saver for allies). It is also the only profession that gives you an advantage if you want to do some PvP. All other professions give BoE stuff which you can just buy if needed.
Being able to disenchant stuff and enchant your own gear is always a nice bonus, but this profession can be replaced by tailoring if you are a cloth-wearing class because of the OP Bloodvine set or the priest robes from Strat living.
Besides these i also plan on rolling an alt with herbalism + alchemy (like everyone on this server probably) to farm a shitload of consumables for raids, because these are really mandatory in vanilla if you want to be a serious player.