A suggestion on how to slightly buff Varus.

Let's just start off by saying that Varus' passive is one of the more, not so good passives for AD carries. Unlike Jinx, he doesn't get a huge boost of speed which helps a lot on marksman with no other forms of mobility. And an attack speed boosts doesn't feel snowball-ish when defeating multiple enemies.

His passive, Living Vengeance, gives him 20% attack speed for 3 seconds on killing a minion/monster, and 40% for 6 seconds on kill/assist.

So he's my first suggestion. Varus' passive 20% to trigger when he procs his W on 3 stacks.

Varus' W allows his attacks to put a debuff on an enemy that when triggered with a spell for bonus damage. This is similar to Vayne's Vi's Ws but with a twist. He has to proc it with a secondary ability. Not only is it more difficult to do this on a carry with no mobility, he has to also land a skill shot spell to do so. It's already less desirable than Vayne's and Vi's. The only advantage is that he can stack it on multiple enemies from a range.

During a teamfight you don't always have the option of killing a minion or monster. Sometimes you're fighting in the jungle and camps are cleared (plus you'd want to be attacking the enemy anyways). Or a fight can occur next to the baron/dragon pit. It would be nice to have a way of procing it before it feels too late for the passive to be useful. It would make both his passive and W abilities feel more desirable and wouldn't make him over the top overpowered.