People complain about poison thieves. Guess what, there are a number of bugs found related to poison.

People complained about Amora being overpowered, repeatedly being told they were wrong. Guess what? There were bugs in the druid class.

I'm sorry, but having fought Amora and had her taking scratches from my hero paladin's wrath, scratches from a hero invoker's geysers, and meanwhile her hunt dealing mangles and being generally tough, I know there was a game balance problem.

So Yanacek may be a very skillful player, but it doesn't change the fact that there were bugs related to poisoners, and similarly druids and Amora. It's hardly surprising that when so much new code goes in it takes time to root the things out. Imms are not going to discover all the problems in a few hours of testing, compared with players putting in hundreds of hours in a wider variety of situations.