Things that really "Grinds my gear"

[Elim]

Healers DPSing?

Welcome to FF14, where only bad or lazy healers don't DPS.

[Slirith]

-Tanks pulling large groups of monsters with only melee DPS w/ minimal aoe capability
-Tanks doing the exact same pull a second time with melee DPS w/ minimal aoe capability...

Those two I loathe immensely

[Wobble]

People that use mounts between harvesting node, I mean come on as long as it takes you to stand there and call it you could have been half way to the next one...

[bloodSp3c]

the frustratingly ridiculous amounts of fucking RNG used in this game!

[Elazu]

-Healers not dpsing
-People who think healers should never dps
-Ninjas not using Ninjutsus
-Ninjas who put down single target Dotons
-Bards not singing
-Monks attacking from one side only
-Tanks spinning mobs around
-Black Mages spamming Blizzard with full MP
-Dragoons not using Heavy Thrust

[Sessurea]

I guess gear grind grinds gears? xc

[Mikita]

Melee DPS who get the bomb debuff when fighting Amon in Syrcus Tower, and remain oblivious to the fact that their explosions are damaging everyone else and pushing people away from the boss.

[Neriam]

Healers who forgets that Amon's debuff can be esuna/leeched

[Wobble]

Melee DPS who get the bomb debuff when fighting Amon in Syrcus Tower, and remain oblivious to the fact that their explosions are damaging everyone else and pushing people away from the boss.

Healers that don't realize you can esuna/leeches that off.

[Kiara1]

When I as a caster needs to use lb cause the melee doesn't (although I admit the few times I play on my melee jobs I can forget the lb too)
When I decide to go as X job, and then I get a bad tank/dps/healer and wish I would go as that job instead.
Joining a "going for the kill titan ex, know strat" and half of the people don't even know what to do after heartphase.

and my biggest one, it will almost make me angry.
People who play blm and don't know the rotation. It has the easiest rotation in the game, and some people still can't do it. (using transpose instead of fire 3/blizzard 3, I actually saw one blm who initiated every pull with flare)