I'm still learning how to play my role as a tank and because my FC is fairly small (though I'm in a larger LS) I generally run everything through DF. I've had mixed experiences with it, but I've never had people bail on me. There was an instance where someone got loot, and they were unresponsive for quite some time so I proceeded into the boss room. Of course I got slurred at, but hey they didn't say they'd be gone and they were given ample time to switch to the gear they looted if that's what was going on.
In any case, the only time I've ever had to abandon a duty was in learning the fight against Titan. One of our DPS's kind of lost it after the third wipe (despite the fact that we kept getting better with each attempt). We were all learning the fight except for the dps it seemed. Either way the other two players were very nice and understanding of the situation, and actually complemented me on my tanking (which is always a plus).
Despite what I've read in the forums, I make sure that I let people know whether it's my first time running a dungeon or not, and offer whatever help I can for first timers. I find that communicating what the needs of the party are at the beginning help make a dungeon run all the smoother. There are times where there is a language barrier (despite region settings and all that), or some players just aren't inclined to speak much.
Overall I haven't had anything I'd call a bad experience. I always ask if there are ways I can improve, or if I should change the way I currently do things. As a tank it's easy to be versatile and we do kind of set the pace for progression.
TL;DR
It pays to be patient and to communicate.
