As some guy above me said.
Varus' problem is his steroid, it's complete trash, the bonus is trash and the duration sucks, you can keep the trigger passive on kill it even fits his lore only if it makes Varus overpowered for the duration, that's the only way it would work out otherwise his passive will keep being trash.
Also the he falls off late game because he's immobile with average range (575 range means jackshit late game) his Q is all his damage late game and it falls off hard, his E completely sucks, it has mediocre utility and does no damage after early game (honestly this ability should be buffed, either more utility or more damage, right now it's completely lackluster). His W although good, it's not worth taking a whole ability slot for it.
So only his Q and R are awesome (W is good btw, just not worth)
His cooldowns are ridiculously long, i mean Fizz's E has a 6.8 CD max rank and it has less CD than Varus'Q and E despite trollpole being such a powerful ability.
So what does that leave us? a unreliable champion with no niche and is outclassed, that takes practice to make the best out of him but you still feel unrewarded because you can't rely on your own ability with him.
(God i have near 1k Varus' game between this and last season and i still feel like i waste my time playing him sometimes)