Basically a lot of things are viable, and many teams have their own favorite champions. There also is a certain difference between regions, as there are champions that are played a lot in the USA, but rarely in EU, and vice versa. And there is a tendency towards a little less variety in big tournaments as some champions are just exeptionally safe choices.
As there is frequent change and many personal choices even amongst the very best teams, it is often not as easy as just creating a "tier list" and rate all champions in power.
Brand, Orianna, Karthus, Anivia, Annie, Cassiopeia, Gragas, Malzahar, Morgana, Rumble, Zilean.
- Orianna is considered a "must ban/firstpick" champion right now.
- Morgana is very popular on EU since her last buffs and by some considered a ban/firstpick champion. She is a durable and hard to kill/gank/outlane laner while beeing a scary opponent in poke fights as well as having massive AoE.
Not so common/subpar APs:
- Zilean is a very "American" choice until now, but proved it's effectiveness during Gamescom. Wether he will become as popular in Europe is not as clear yet, but so far he has rather been accepted as an additonal choice amongst many, especially since he is strong early but especially weak late game.
Akali, Kassadin, Mordekaiser, Galio, Ryze, Kennen, Heimerdinger, LeBlanc, Lux, Vladimir, Swain, Twisted Fate, Karma
- Akali is still beeing used by some teams as an AP and is the most common choice amongst these for tournament games.
- Mordekaiser suffers severely from lack of crowd control abilities compared to other APs, but still is a viable choice for certain team compositions. He is mostly considered to counter AD carries due to his ultimate.
Ashe, Caitlyn, Ezreal, Kog'Maw, Tristana, Vayne, Miss Fortune, Urgot
- Kog'Maw is the most banned AD carry right now as he deals tremendous damage on high range.
- Miss Fortune is the probably least favored AD out of these. She is close to Kog'Maw in style but has severely lower range.
- While Ashe usually plays a defensive lane style with a supporter like Janna, the other ad carries can play aggressively depending on their supporter.
- Ashe and Tristana have the weakest midgame but strongest lategame.
Not so common/subpar ADs:
- Urgot is the most recent addition. Long not considered a real ad carry, Fnatic Lamia and #1 EU solo queue Yellowpete use him to great effect. His ultimate can give him guaranteed kills during ganks.
Corki, Sivir, Twitch
- Corki gets outdone by most ADs since his blind was removed.
- Sivir and Twitch are very niche champions, though not unplayable.
Sona, Janna, Taric, Alistar, Soraka
- Taric and Alistar support a highly aggressive playstyle on bottom lane and are more favored since Riot lowers heals and sustainability.
- Janna and Soraka are the more defensive picks, Soraka gets severely less attention since her skills were changed from sustainability to a more burst/counterburst playstyle though.
Not so common/subpar Supporters:
- Sona supports a harassment heavy playstyle or protects against such.
Basically anything that just adds harass, and Karma.
Irelia, Lee Sin, Gangplank, Cho'Gath, Jax, Nasus, Singed, Talon, Trundle, Udyr, Warwick, Garen
- Irelia and Lee Sin make specifically often picked or banned top laners in Europe right now.
Specific AP Toplaners:
- Cho'Gath makes many appearances in tournament play in general as a solid choice.
Nidalee, Rumble, Kennen, Galio, Heimerdinger, Akali
- Nidalee is a frequent pick in tournament play for top lane, as her spears make her one of the strongest poking champions. She suffers from a recent nerf of her heal though that makes her less sustainable.
Not so common/subpar Bruisers/Toplaners:
- Kennen and Galio are rather typical for American gameplay and way less used in EU.
Dr. Mundo, Jarvan IV, , Olaf, Pantheon, Poppy, Renekton, Tryndamere, Wukong, Yorick, Xin'Zhao, Blitzcrank, Kayle
- Jarvan was an extremely common choice until he got nerfed repeatedly and is rarely seen ever since.
Amumu, Lee Sin, Udyr, Nocturne, Alistar, Trundle, Warwick, Gangplank, Fiddlesticks
- Especially Amumu but also Lee Sin make an extremely frequent ban. Amumu is known as trademark European and considered one of the strongest champs of all in Europe, getting banned on every Elo and level of play for his amazing CC ability. But he is specifically dependend on blue buff while beeing a poor lv 1 fighter, so lv 1 invasions are often seen against him.
Not so common/subpar Junglers:
- Fiddlesticks is known as a typical American champion and finds way less recognition in Europe.
Jarvan IV, Malphite, Nunu, Olaf, Rammus, Shen, Twitch, Evelynn, Xin'Zhao, Shaco
Bans or firstpicks extraordinarily often include:
- Orianna, Amumu, Brand, Gangplank, Morgana, Kog'Maw, Irelia, Nocturne