Not a single unit in this game has not been bitched about, If one PERSON in the community was to say a "flame pio" is OP just because someone got lucky with RNG and wiped a whole squad, everyone would make threads about it until it got nerfed.
I think this is the case for all game communities, especially those with a competitive or multiplayer element. Ultimately the feedback in the aggregate is useful. Not every post is, but if lots of people are posting about one unit it ensures we take another look at it.
We listen to both the top tier players and more casual fans, because ultimately the game is designed for both groups. Top players, typically those who are in tournaments or at the top of the leaderboards, tend to know the game better than more casual fans and can give a different type of feedback. But that doesn't mean we should ignore other fans.
I'm not sure if Blizzard specifically has side-conversations with the top tier SC players, but I'm sure they're monitoring their feedback and I'm also sure that they are aware of what their casual fans are saying.
I know that's the case on EA SPORTS' titles, though they're not quite the same in terms of competitive esports.
In terms of what's wrong with CoH 2 and blaming that on the community? I don't agree. I think that you over-estimate the herd mentality of the community. I think if someone started saying that the Pios w/flamerthrower were too OP and were taking out tanks, people would mock them.
However it could be what's wrong with the game to you. As Miley Cyrus famously said, "There is nothing either good or bad, but thinking makes it so." If you don't like the community then that could ruin the game for you. There's some FPS games that I won't play multiplayer because of the community, and so I've stopped buying as many FPS games.
In terms of whether the community makes the game better or worse, I think it only makes it better. When we fail, and we have failed at times in the history of the franchise, that's on us. When we succeed it's because we've had really great support from our fans.