- Do mercs help get you out of his lifedrain move faster?
His only (direct) "lifedrain move" is his ult, and you get out of that by just not being near him. The ult itself does not apply any CC unless he has Rylai's.
Merc treads will reduce the length of his snare (W), but if you get hit with that you're already in a lot of trouble if you're squishy. Swiftness will reduce the amount of slow on his Q (and his E/R if he gets Rylai's).
- If no one on your team has ignite, what item do you buy to reduce the power of his ult?
Morellonomicon/Executioner's Calling will reduce his self-heals. So will buying MR, since he deals less damage to heal off of.
- What items are recommended to stay alive against him? I went the wrong build and it cost us the game, but I don't know what the right build was. :S
Things with MR. Or you want to try to burst him down. It's hard to win a sustained fight against him 1v1, since he deals amplified damage to the target of his E and he's constantly healing back up if he has his ult toggled on.
As Vi I'd be looking at Hexdrinker/Maw and Merc Treads, probably... not the best matchup in general, since Vi is more of a sustained-damage tank buster. Gapclosers aren't that great either, because he'll just DOT you up and snare you after you Q in, then walk away. If you can catch him out at medium-to-low health with his ult off, try to R->Q->E to stunlock him for a couple seconds. Unless he has a Zhonyas that will probably kill him, especially if your laner dives him too.