I'm sick and too lazy to bother going to use the Will Smith 'tada' meme generator, but imagine one of those right now with "the thread about the mentor system being broken" as the target of the 'tada'.
I mean, you're 100% right on this point, but there's literally a thread even longer than this one talking about all the reasons people
don't help each other as easily/smoothly/often as they could in the game. People don't accept advice readily so it's not given, people are rude so folks don't ask for advice, mentors are terrible, players are terrible to mentors, it's Tuesday, etc. So, yes, point entirely conceded, but it only raises another potential place things could be smoothed out and improved a bit.
And even still, I feel that adding content that helps with, say, the slightly more advanced concepts of tanking—or at the
very least explains the aggro table—would not
hurt the situation, even if there's other ways to address it.