S5 has been only 1 meta

It's not the tank meta or the juggernaut meta. It's the hypercarry meta. On almost every winning team there is a hyper carry. Over the course of the season we have seen different strategies and team comps designed to beat hypercarries, such as tanks bruisers and juggernauts. But these have all been reactions to the power and prevalence of hypercarries in game. So we have been misnaming the meta, and therefore losing focus on the issue. By their very nature Hypercarries are difficult to balance.

Now I'm not saying that riot has not introduced non hypercarries who weren't overpowered. While Juggs are in a good place now they were OP when they were released. And I personally feel that tahm kench is too strong as well. But that is because he provides so much protection for these hypercarries. Anyway my point is that the rise and fall of viability to some champs does not define the meta. It is the unchanged aspects that should deteermine that.