ProjectOMS

Well it wasn't so much a party class at the time, but they were the best defensively. If nothing else, Paladin's defense and blocking ability allowed them to handle party organization things at Zakum and such without as much worrying about dying if parties had to be remade in the middle of a boss fight. I suppose other warriors could do it too, but Paladin easily had the highest defensive power.

...nowadays, potential makes it easy for various classes to cap defense, and classes like Wind Archer get -30% damage intake...in third job.

While true, Defense didn't mean anything Pre-BB. Only after Big Bang did Defense actually mean something.