Is varus till viable adc?

I mean he can work because soloqueue allows it, but there are way too many better choices.

"Gameplay" I'm assuming you are asking for yourself, and not in a ESports sense, right? Yeah, he is just fine, go ahead and play him if you like him.

I was still doing fine on him in Platinum during the pre-season. He's fine for seiging and teamfights but his lack of mobility and dependence on mana can be a hindrance.