I've always thought Varus is a pretty cool champion. I think his biggest problem right now is that he doesn't really have a niche. If you want a lane bully, there are much better options. If you want raw, late game carrying potential, there are much better options. If you want safety, there are much better options. And if you want utility on your ADC, there is a better option. People rag on Ashe a lot, and she does deserve a buff, but at least she has a clear niche--she's the utility marksmen. Regardless of what you're looking for, there is always a better option than Varus.
If Riot is going to buff him, I think they should look at his Q. It's a really cool ability on paper, and it seems like it should be the defining aspect of his kit in lane, but it's just not good enough. Sure, it does a lot of damage when it lands, but it's heavily broadcasted, easy to dodge, and deals pretty low damage if it passes through a minion on the way to its target.
I mean, hell, when he saw a brief spike in popularity back in S3, people weren't even leveling his Q first. As I recall, they were leveling his E (? could have been his W) first for burst during trades.
Some buff to his Q (either its reliability, or its power when it does actually land on a champion first) would help give him the niche he needs.