Ehh, I agree people tend to overreact. That much is a given.
But people who write walls of text are usually just extremely passionate about that character, and that's why they talk so much. I think any sensible person should see current complaints as first impression type complaints (and that's likely Riot's current approach, too).
I'd just like to point out that people complained that Vel'Koz was OP and needed nerfs when he was launched, and if he's seen any competitive use, I haven't heard about it. So people can be wrong both ways. The only way to really be 100% sure of the impact of a rework is to push it to live and wait about a month for people to get used to it/pick up on good builds/discover new methods of play/figure out how to play against the new kit.
That doesn't and shouldn't stop people from giving their $0.02 about champions they're passionate about, though.
My only real criticism isn't even the rework itself, but the silence on the PBE. It felt like the Nidalee rework had a lot more conversation going on, and even if it's just to say "we understand but data says otherwise", it helps to know they're reading. The long silence created a lot of anxiety and that seems to have carried over to live. A lot of the exaggerated reactions stem from the fact people have been saying the same thing since the PBE, with no* visible* effect. It doesn't mean they weren't heard, just that they didn't feel like they were.