There are good reasons the champions that get played in the LCS are played in the LCS. It is true even pro players have limited ability to practice and employ more than a handful of champions to their standards as a group, and that most off meta champions aren't necessarily terribly off the radar. However champions that rarely see play have challenges that often exceed their rewards. So when you have to prepare something for the stage and scrim for hours as a group with that your theory behind the pick has to be solid, and your performances in practice need to be promising... anyways.
With really braindead and oppressive stuff like Azir and Vladimir in the mid lane right now the bar is set really high in mid lane in this meta. Of course when Riot gives Viktor the ability to one shot waves with a single laser back ofc he became meta again after being top dog most of last year. Viktor does have a kinda slow presence early game for solo queue regular play, but he scales really hard and reliably due to one of the most powerful traits in competitive play: waveclear.
Just because Keane got beat by a better player on a better team against another really strong champion (Taliyah; anyone with a brain woulda realized this would soon be a power pick in pro hands) doesn't mean Viktor is balanced lmao. S5 mid was basically the Azir vs. Viktor show (part of the problem is Azir crowding out and dictating mid lane meta)
While not necessarily true, I lean more towards the belief that just about everything played in the LCS is overpowered. But I'm not a meta sheep. I has my own op pocket picks that I know when they work best.