I run a quick check at the start of the dungeon.

Does my healer have over 4300 hps?
Do I have a BLM, SMN, or BRD?
If the answer is yes, I ask the healer, "You like em big?"

Does my healer have over 4300 hps?
Do I have any 2 of the following: BLM, SMN, BRD?
If the answer is yes, I tell the group, "Pulling lots."

Do I have 2 melee in the group?
I ask the healer to dps (if they aren't already in Cleric) and I throw on full STR set and quickly single pull with no breaks.

Do I have multiple new people or under geared people in the group?
I throw on full STR set and single pull, while adjusting pull speed and size based on the group's performance.

Is the dungeon Aurum Vale or Dzamael Darkhold?
I teach the group how to sac pull these dungeons.

I understand that there are probably a lot of tanks out there that either don't care or don't know how to adjust due to party comp, but seriously... Quit whining. Learn how to take the good with the bad. I'd bet a million gil that you meet way less doodoo tanks than the amount of windowlicker dps we run into on the daily.

Gripe at SE for poor quest design, or thank them for a coming up with a very clever way of getting faster DF queues. Lots of us are working on our Zodiac weapons and this pretty much sums up my thoughts on the subject of slow dungeon runs:
https://www.youtube.com/watch?v=zGxwbhkDjZM