Top is Sion/Urgot/Aatrox however there is still Sylas, Akali, Jayce, and Ornn played.
Jungle is Lee Sin/Xin/Camille but we have Karthus, Olaf, Kha, and Nocturne.
Mid is Lissandra/Galio yet there are picks in Zoe, LeBlanc, Cass, Ryze, Karthus, and Orianna.
ADC is Ezreal/Kai'Sa/Lucian -- although there was some Draven and Viktor early, not as much Sivir as expected but still a pick.
Support is literally just Braum/Alistar/Tahm/Thresh every season. Zilean and Rakan are possibilities sometimes.
There is a high volume of central picks, and if a composition does not favor them or a ban phase makes it difficult, there is another small pool. Risk aversion is generally the rule, but consistency is the key. You want to be consistent, and most of these champions either are, or make it difficult for another champion or combo to feel safe.
The game has become so snowball oriented because of how you can punish if applied correctly. Take Faker on Zed. He can certainly pressure most pro mid laners, we know he has the mechanics to even be able to possibly solo kill. But, what if it doesn't happen? There's no guarantee and there's no leeway anymore to allow that because even if it is possible that he beat the enemy mid, things can go wrong regardless of how strong he or the champion seems, and then you just lose because so many things on the map can be punished. Your jungler relies on mid more than ever now and will become useless without your help, there's a Rift now on top side, there's RNG dragons and scuttle vision, there's Baron, there's turret plating gold, and then there's incredible item scaling. You can't give any doubt.
Galio/Camille though? Very small margin of error. It works, and while it may not have as many rewards as Faker 2-0 on mid and oppressing the enemy mid early so you can pressure the whole map, it gives you free pressure even if you do nothing but press R. Pressing R for + is much more consistent than pressing R and needing to actually do things.