Why do people avoid getting better at the game?

[Gemina]

Having a third DPS is the EXACT purpose of this, if you do not require a healer you bring another DPS.

But sure, jump over to Materia with your level 90 healer and lets do this.

Well, it would seem DC travel is not possible for me outside NA DCs, and I cannot visit Materia, nor you Aether. What I will do is at least provide the dungeons I planned on going into. I also never planned to make this impossible. Only difficult to obtain the clear without heals.

ARR - Wanderer's Palace HM: The last boss uses doom that can only be cleansed by healing to full. The effect can be avoided if not looking at the boss when he casts the ability.
HW - The Vault: Charibert simply requires heals as his auto attack damage is constant on the tank throughout the fight. Probably still possible as WAR since you do have Equilibrium and Raw Intuition, plus Invuln going into this fight. I was really, really curious about this fight in particular.
SB - The Burn: Pretty much self-explanatory. Without heals, Rime Wreath spam, which is unavoidable will eventually kill the DPS jobs and the healer. Mist randomness can make dodging a little tricky. The tank might be able to sustain themselves, but will be rough taking the creature down once everyone else is dead.
ShB - Amaurot: Last boss is similar to Mist Dragon threat level.
EW - The Dead Ends: Need to avoid mechanics from first boss. If inflicted, not having Esuna will kill the player. Same can be said for any boss that uses a doom mechanic really. Skilled players won't have too much issue.

TBF, just this morning I was in DF for 90 dungeon and we 3 manned it when the healer D/C and never got the healer replaced. WAR absolutely does not need a healer in any of the 90 EW dungeons and can go 1 tank / 3 DPS pretty easily. This isn't a brag, just that any tank with a basic understanding of their toolkit can probably do without a healer if they were so inclined.

WAR healing is ridiculous, I'll back step a little bit and admit that for sure. They can even do heavy trash pulls without much assistance from the healer. However, putting skilled players together will always make things easier. That is a given. The thing is, you're run of the mill average PUG party is going to have wide range of player skill levels. Majority of groups are going to need a healer to fix mistakes, and that's the point I'm trying to get across. How much they are needed for dungeons is going to vary from group to group.