If you are a [JOB] without [Ability], you are holding back your team at endgame

[MelianDoriath]

I don't quite agree on Mercy Stroke. Usually on a boss that is near death on my Monk I can get it to hit for ~500-600 as a crit, which is quite a significant bit. It even beats out Snap Punch, which is probably the hardest hitting Monk skill. And it isn't always a "use once" mechanic, I've found time to use it twice on quite a few fights, most notably Cadeuceus in Turn 1 of Coil.

Mantra is an amazing skill when it's from a Monk. When it isn't, it's kind of just a nice skill to have.
Also: You left BLM off your list

[Hachiko]

I don't quite agree on Mercy Stroke. Usually on a boss that is near death on my Monk I can get it to hit for ~500-600 as a crit, which is quite a significant bit. It even beats out Snap Punch, which is probably the hardest hitting Monk skill. And it isn't always a "use once" mechanic, I've found time to use it twice on quite a few fights, most notably Cadeuceus in Turn 1 of Coil.

Mantra is an amazing skill when it's from a Monk. When it isn't, it's kind of just a nice skill to have.
Also: You left BLM off your list

It's justifiable as a monk because there isn't a 5th skill to really cross class. Same with Dragoon. But it's definitely not great. Even if you crit twice, you're still talking ~1000 additional damage over what is around a 7 minute fight.

It works out to ~2 additional DPS. Yes, it's more than nothing, but it really isn't something that is really necessary to go out of your way for. Yes reducing it to dps is a little 1 dimensional because of where the DPS comes, but the point is it's hardly a necessary skill. Comparing it to say, Blood for Blood or Internal Release and it isn't even in the same ballpark.

Maybe I went overboard with saying it is completely pointless, but my point is that it's definitely not a necessary cross class skill. Not like Swiftcast, or Blood for Blood, or Provoke, etc.