Persnally, i would say pld and sch are my main. i finished relic for both. i do play others but those are my fav. but for sure if i go DF i never need to use Tank unless i am helping someone in FC for their expert , or if i go raid.
the only time i ever felt the need to do on PLD in DF alone , was when i was doing Atma or when i was leveling. going on SCH in a dungen is a much more relaxing experience for me, as i dont have to worry about agro or other dps pulling stuff before i get to flash them etc.

i did do a little brayfox farm back in the day for alexandrite, but only in those 4:30 2 boss parties with some friends or farming linkshell.