I imagined the new classes as a class all ready to go (Job Spec), the only real way to learn it is to play it, unlike the standard classes where you start at 1 and level to 50 learning as you go, the new ones drop you right in it.

I played a DRK a bit and from just the lvl 30 skills it plays very much like both PLD and WAR.

Your basic 3 skill combo, a paried attack, aoe and ranged single aggro attack. "Auras" to boost abilities (attack vs aggro + defence) although you can use both.
As always though, FATE grinding is the most effective way to 50 (as I've experienced) after 50 though I have HEARD dungeons are much better.