I leveled a lock to 70, and have a baby trio atm. I'd say take imp corruption, destruction up to shadowburn then back into affliction. Max out your drains, inc imp drain soul (gives mana back if you kill the mob during the drain, and its more than the cost of the spell) Get yourself a mod that limits the number of shards also, so you don't fill your bags up with shards due to draining. Basically your gonna end up dotting everything, but you'll have shadowburn as an Oh Shit insta cast nuke. Demo to me would be a waste with a 3 crew, can burn much faster with dots and shadow bolts, and you'll never run out of mana or health once you get a clue as to what your doing. I seriously never carried water or food until I hit outlands leveling with affliction.