I don't think anyone has mentioned the main point yet.
In tournaments, or any high level play, it's going to be a team selection similar to DotA, yes?
The minute active counterpicks are entered into a closed system like that, it permanently borks the tier ratings. And the math just ripples through and grows exponentially. I would imagine it's possible to pick hard counters for far over 50% of the possible choices in the game if you're judging it at the level of individual selection.
Lets say you pick what is generally considered to be a top tier character. If I've got next pick, and I pick a hard counter to you, does it matter that the hard counter might be a lower tier? Somewhat, but minimally, at best. What if it's a hard counter so powerful that not only is his guy > yours, but it FORCES someone on your team to pick a hard counter for him? Yikes. Gets gamey fast.
Most games are going to revolve around team synergy; pick a gimmick or two to build a team around, or an overarching strategy to build a specific team around, or a combination of a few key abilities to build a team around and you may throw in a few hard counters, depending on how things go down and how many of your slots are devoted to the above decisions.
Tier = pointless, here. If you're going to 'compare' heroes against one another, the only honest way to do so is (surprise) the way the game is designed. By fighting specific 5v5 team matchups against one another.
Once you're at that point, player skill becomes the differentiator, along with the theorycraft, item choices, and all the other things. But tiers are pretty weetodded for this, no matter how you look at it, and of practically zero use.