Importance of Cross-Class skills

Mercy stroke is ok. I have it but I don't actually slot it. Stoneskin is fun because I can find interesting places to use it:

I'm OT, and MT is about to take a big hit or healers are getting behind.
Someone just died and I want to help them out after a raise.
I'm OT and about to swap in for MT.
I'm MT and the boss is wasting time not attacking me (Titan is jumping/landslides, for example).

My favorite was putting up a stoneskin on the demon wall right before it repels. I watch the rest of my team go flying back while I don't budge. Everyone kills that too fast now though. :)

Learning when to cast Stoneskin between Autoattacks, etc. is also fairly key to making it more useful.

For solo playing like maps, quests, FATEs, etc. Cure and Protect are very useful, but not for group content, you'll have to change cross-class skills.

Mercy stroke is nicer than it looks like, it's an extra attack, and with trash mobs from time to time you get a heal. Not essential.

Stoneskin is important in 8 man content when there are tank swaps, and occasionally other times. Everybody thinks a PLD should have it.

I use Foresight and Bloodbath too. In group content I take off Cure and put Mercy Stroke and vice versa, you can occasionally use protect on some raised player or yourself if the healer is very busy, but a PLD does not use cure in group content.

What about Fracture? I keep it when im off tanking to spam more damage, I think is a nice addition.

Facture is good, but u have to manage your TP comsumtion. it eat a lot of TP

I'd consider Mercy Stroke before Fracture. While Mercy Stroke has much lower uptime, it is free and oGCD. If you're looking to increase the damage you deal you want to grab options that have the lowest negative impacts on your play, which is Mercy Stroke.

As for the original question, I personally would side-eye you for lacking either skill and there's little stopping you from getting both.

tbh, PLD cross class. there not much choice for end game ><

From CNJ,
Cure - not really useful, and it getting worst once you get Stone Skin. lol
Raise - not useable in - combat. so not really an option for End game
Stone Skin - really nice to have, can be useful in various situation. I mostly use it for when DPS got Res, Stone skin give them a decent buffer for their missing HP.
Protect - for solo content mostly. in End game Raid 99% of SCH will pickup Protect from CNJ anyway.

From MRD,
Mercy Stork - Free DPS, Off-GCD
Facture - DPS increase at the cost of more TP consumption.\
Foresight - a nice 20% increase in Defend,
Skull Sunder - Useless lol, PLD has the similar skill call savage Blade. (this skill prolly made for future Job)
Blood Bath - minor Self-Heal and small enmity boost, nice to have.

The thing about PLD is that PLD job is viable on it own, and not relied to much on cross class skill
Unlike WAR, where they Require to have Provoke from PLD.

Especially in T5, Stoneskin will save your ass from Death Sentence.