the trouble is that you are too focus on FF11...
thief are commons in Eorzea... they are far to be a lost art... people can argue for hours... but you have a high probability that thief will be a class more than a jobs... (rogue is the same thing only with a different name)
what you will do as class for thief? scout? ohh great you use dagger and learn to be elusive and.... that all... you need to bring mechanic in a class... and personally i don't see what can bring Thief as jobs... steal? we can't steal item or gils from monster or it will be a huge trouble for them economy. sneak... no sneak nor invisibility for the player. (outside the one gained in the quest for do it) if you look like this...the thief will be a really really poor choice as jobs... don't hope too for treasure hunter passive, since the treasure hunter it's a mini game. as i see it... the thief don't have a lot for him.

finally, this is final fantasy 14, not final fantasy 11-2...