So I can not say as much about PLD as i am a WAR, but what I can tell you is ever as a good experienced tank, there is often little you can do when your party you get from the DF is not that good and do things they shouldn't.

When I run with FC i can do a single overpower and a single flash (and maybe a few parts of a combo on side mobs now and then) and everything stays glues to me because my healer isnt overhealing, my dps follow my targets (no you dont need marks to have this work), if I loss threat they dont run away, and people do their jobs. Now when I pug with DF... well.. sometimes I make things worse by trying to be the good tank and tank everything. The thing we all need to learn is that, for at least trash mobs, if one goes off and you put all your attention on it and lose the other 2 also it helps no one (and often leads to even more of your bad tank chat BS).