I've seen this a lot after you used it... in fact, I wouldn't be surprised to see Sub-Gastly become the most common set for him. =0I am currently using Gastly to replace Missy and I am having great success with a moveset of Substitute / Thunderbolt / Sludge Bomb / Shadow Ball and an EV spread of Timid 36 HP 36 Defense 196 SpA and Speed. With it's outstanding base Special Attack of 100 and a decent base 80 speed it can break holes in teams and help some of my other sweepers (DRATINI). It can also use priority with Sucker Punch that with Life Orb doesn't do damage too shabby. For my team Gastly has performed better than Missy which is awesome.
@ Dub: I see... okay, fair enough. (er, and... I count four moves in the Liam Lord's set. =0)