Every time someone says "the DDs need to learn to hold back a bit" they prove the case that Paladin is inferior.
No one here loves Paladin more than me. (>.> ) Equally, maybe. More? No way. And it's inferior.
If you have to say "Well, if the party has a Paladin, as opposed to a Warrior, they need to learn to pace themselves", you just made the case for Paladin being inferior.
DDs do not need to pace themselves with a Warrior the way they do with a Paladin.
To OP: Paladin can Stoneskin, a well-geared WHM can do it better. Other jobs present - BRD and WHM, or anyone on a Class instead - can give the tank Stoneskin. It is not of great import for Paladin to have access to it when others will cast it on the Paladin routinely.
And I second Phobos' groaning about the idea of balancing jobs through content. That's not repairing what's not working with the job, that's tailoring new content to bad mechanics. That is what FFXI did for the entirety of its existence.
Don't do that.
Lastly, I do not want to come across as unkind, but the truth is that there is no skill involved in getting Stoneskin up before Hellfire, as a Paladin. You have sixty seconds before Hellfire, after Nails pop - you start a timer, you won't be caught off guard.
If your best point about the defensive potential of Paladin is being able to survive a scripted sequence attack with a minute of warning, then this thread is simply pointless.
Also, Stoneskin isn't native to Paladin. (>.> ) It's not a "Paladin defensive ability." A Gladiator can do the same bloody thing.