I have a 50s in PLD, WHM, and NIN (among others). I rarely will tank DF. I will tank for my FC and Friends at that drop of the hat. I have found that players in a DF (in general) are not the kinds of players that I wish to associate with. I think it is not the content, but the "No consequences for my actions as I hide behind and avatar" mindset that turns me off the most.

I play to have fun, Tanking the DF for me is not fun, so I do not do it.