When do the training wheels come off?

[Azbroolah]

Decent gear - when you are low level, spamming dungeons, you can often move up several levels and discover your gear is less than optimal, but sufficient anyway, you just move on.

Are you seriously saying I should spam something like the vault until I upgrade all my gear, and only then move onto great gubal library?

No one does this - you spam the vault a couple times to reach level 58, then you spam library, and whatever gear you get along the way is bonus.

You're moving the goalposts here. The tank in question was using a level 15 shield in a level 44 instance, not gear from the previous dungeon. There is no excuse besides deliberate laziness for using gear that is almost 30 levels too low.