Which is all well and good, but how?
How do you know if someone is gemmed badly? and more to the point, do they know they're gemmed badly?
Lets put idiots being idiots to one side for the moment; how to you teach someone what's best and what isn't when they've never needed to know before now? How do you design a system which gets that across, rather than just punishes someone, for something they might not realise they're doing wrong.
The same goes for poor performance, what makes you think they've got meters? What makes you think they know they're being bad?
Outside of the meters (which are optional...) if I levelled a monk tomorrow and started killing things / completing quests, what measure is there to tell me that I'm doing badly? Of course there are places you can read this stuff, but again, why would I know I needed to read up if I don't know I'm doing badly?
Are there any other examples of games outside of MMO's where you have to read up on a 3rd party site what you need to do in order to play the game "right"?
It just goes back to something I think blizzard should have added a while ago, training, which is even more important now that casual is the way they're going. Simply throwing new spells at someone every few levels doesn't teach them how to use them and there's simply no hints in the game of the order / priority that these things should be used.
Again this is the royal 'you' rather than the finger pointing 'you'
What you said makes total sense and I'd love for something like it to exist but it needs to not just be a stick to beat people.