LEgionDark
Since, FM has been brought up. I will basically tell you that FMs can do a decent job at Dungeon Runs, Farming, and even Colo Runs.
On the other note, lot of players would suggest other classes, base on the point of...1. They are more faster during one job. 2. They would base that on the concept of Dual logging. In looking at the run end, everyone knows that FD gear is the strongest gear. But, it is truly very costly price tag especially if you are aiming all 8 classes to be FD, since FD Gear characters are basically unstoppable unlike the non-donor character.