Hmmmm... dunno about you OP, but I LOVE to look like an elegant baus while tanking. Heck, to be honest, I like all the robe styles of the various job classes. Its an intentional art style that translates with the theme of Eorzea
And like Felis very rightly said, they are long coats (+1 to you for that)... the coats are generally also referred to as surcoats and have been worn by knights and elite mounted calvaries since the 12th century. Also, any self respecting Final Fantasy fan will realize that this long coat style has always been one of the main styles traditional to the series.