What is involved in rank quests? Are they just like leves? I figure each class has different task. Does anyone have examples?
Yes, they're different for every class. Totally different from leves. They involve storylines concerning each guild/class. In the glad quest you fight some, the weaver and goldsmith require you to craft something (the recipe seems to be nearly guaranteed), and the miner quest requires mining from three different areas. They also have instances and usually some sort of cutscenes.
They are definitely at Rank 20 and 30, and most likely 40 (if the pattern continues). It seems the data only has 3 for each class.
Also, it seems Armorer and Blacksmith share their quests.