Inside POI quest there is a room with 4 paths, 1 for each vocation. It is not "blocked" for other vocations, but there is a fire on the floor that deals increasing damage, each SQM you walk further (if you are in the path for another vocation).
I'm an EK and I once had to pull the RP lever, since I was lacking one, and in the last fire I think I received around 10,000 damage.
So, in a way, this kinda counts as "blocked" for most people xD