Titan HM is an example of why you should be able to edit the duty 'set-up'

There are no responsibilities for the second tank in the fight other than to serve as a weaker DPS. There are no stun responsibilities like in Ifrit that can be handled, there are no adds. There is just the standard Tank, Heal, Dodge, Damage - except the tank role is already filled.

This isn't to say the fight is un-winnable with the DF default set-up. But it makes in incrementally harder even when you discount the lack of communication or experience the players in the DF pool have with one another. In almost every situation you will be better-served by a 5th DPS to pass the Heart Phase easier or 3rd healer to survive post-heart phase easier. So why are we forced to be put into this disadvantageous position?

I know some people are going to say "Play with friends" or "Join a FC and do it with them" but realistically the DF should at least be a viable option in terms of party set-up as it is in every other dungeon prior to this point.