I'm all one for team play but I generally like to assess a champs power indivdually then veiw how it will effect the team.
has seen repeated nerfs due to frequently having the single highest win rate of any champion for a considerable amount of time. She went through worlds with an 80% win rate in season 4, and she's hovered around the 55% win-rate, at least bi-monthly, since LoL went live before season 1.
She's a terribly weak champion individually and especially on a support's income, but she's among the strongest champions when it comes to effecting the whole team: and at the end of the day, LoL is about helping your team.
You're setting yourself up to get blind-sighted by only looking at a champion's individual strengths. At a certain point, it's worth planning ahead and thinking about team-combos and strategies. As a 5v5 game with a healthy competitive scene, Riot is very much balancing champions around the notion teamwork is a thing.
And champions with solid team synergy usually just win more games than those without. Monthly win-rate charts usually show common Q_Q assassins sitting at the bottom with the lowest win-rates, where the who's-who of supports and tanks usually appear in the top 15.
My main point here though is effecting the team is a substantial part of champion kit power-budgets, disregarding that entirely is like disregarding mobility or range as meaningful aspects of a kit.
Which leads me to this:
but when he gets ahead he shouldn't fall off simply because the other laner hit lvl 6.
If you don't want to play a champion that's all about playing smarter rather than harder, if you don't want to put up with team-synergy and teamwork, if you don't want to deal with setting up combos for your allies to finish, don't play a tank.
Tanks are so much about team-synergy they work as supports.
She's ultimate is insanely powerful when used well, and it's one of the best ultimate in the game.
If that's not your style and you want to be about the lone-wolf life: Most fighters and assassins are much better 1v1 champions than team-fighters, packing a lot of punch in a duel but often falling short in large-scale 5v5 battles.
The fighter/tank life is just very different from the tank life in how the kit's power is distributed and how you want to play them. While tankyness is a common thread, that's it.