I would be fine, if the game teaches general stuff and adds an class specific mentor chat to the game. But i don't want an 100% bulletproof developer class guide, because i really enjoy the community discussions about classes and i fear that people would get more lazy and don't think about the game as much as they do now, if the developers would interfere like this. I already here the argument "but the developer said..." in my ears xD
The issue with that argument or mindset is that, developers can make mistakes aswell, despite their knowledge about the game being very good. After all they created the game. But sometimes the community finds better rotations or solutions and this was the case with the ninja and then they nerfed the class after stormblood. If there would have been an developer guide, than i assume people would never have found a better rotation or many people would not believe those theocrafters, because the developers found another rotation and they have to know always best. After all they are the developers of the game, right?
Additionally i don't think an official guide would solve the problem completely anyway, because if people dont want to get better at something, than a guide wont help them, since they'll just ignore it. I've seen people getting criticism or insulted for their dps, including some friends. But imo op is right that healers and tanks get more toxic response and at the end of the day the fear of a few people using an feature for sth bad, should never prevent an developer to add it, if most people use it for something worthwhile/good. Might aswell delete the aggro list or chat function or not add the replay feature, if you want to protect everyone. Personally, humans and never a feature can be the problem and you can deal with those few easily by kicking or banning them, if they really harasse people with the information of a feature. Be it aggro list, parser or sth else.