Riot I'm curious how you work with New Champions "Q/A"

You guys create a champion and then release it for PBE, where players give it a shot and then return feedback, on what they think about the champion over all.

but..

From the past 4 champions that were released, the same day they were released was the same day people made an uproar on how unfair or over powered the champion is.

So my question is

Does the Riot Team make absolute sure that new champions wouldn't be too much of an issue before release?