While I agree that folks should stay up-to-date on their class/job quests, I do want to point out that there is NO content from 45-49 that can't be completed with a completely gimpy tank. Or no tank at all. I have personally completed runs of Dzemael Darkhold, Aurum Vale, and Cutters Cry as a three-man party with no tank, and while I haven't actually done Garuda that way, she's been nerfed so hard that I'm guessing it's possible. There's no way that even a terrible tank that can't hold hate for crap is going to make such a situation worse.

By leaving such a group, and accepting the 30 minute penalty, you are punishing only yourself, because you could have instead finished the run in those thirty minutes with the gimpy group you entered with.

My recommendation is, if you find yourself in such a situation, calmly and POLITELY explain to the tank why they're having such trouble tanking, and how difficult it will be for them in the future. Let them know that the class and job quests are not optional content; that they unlock valuable abilities that will make their job a lot easier at low levels and can simply not be done without at higher levels.

As for 50+ content, most dungeons can still be cleared without a tank, but it gets progressively harder to do. If job-crystal-less tanks are still showing up in those instances, it may be worthwhile to bail.

I'd also like to point out that this isn't exactly an epidemic. It is RARE for someone to show up in such content without a job crystal. On the occasions that it happens, it's not unreasonable to suggest that you actually try to educate them.