I'll be the one to defend Hyo Min there and say that jobs, as of Stormblood, have been greatly changed to work differently in PvP than they do in PvE, not entirely for the better. And given how widely people hate PvP as if it's a mark of pride among the community, only those who actively WANT to PvP seek out the information on it. On top of that, nothing beats practical experience. Even if you've seen the job played, that doesn't mean you can play it to that same level from that alone. I might perhaps make PvP MCH look easy (and in fairness, it's a bit braindead in comparison to 3.x PvP MCH), but I've seen and defeated plenty of other would-be MCHs in PvP, attracted by its flash and damage.