Almost all dungeons have a single path. Even the few with multiple paths there's no 'wrong' way to go.
Knowing them is more about knowing yourself, in what you can pull and not die from. Generally this is reserved more for the level cap dungeons (level 50, 60, 70, and 80) while the starting and in-between dungeons for levelling are accepted to be a slower pace.

Tanking is the easiest job in the game while also somehow being the most intimidating one.

I couldn't suggest tanking hard enough for anyone who wants to try. It's a great place to be and puts you right into the combat, makes you feel like you're the main star of the show, which the story does well to compliment.