What i got out of it was unlock jobs allow you to basically lock yourself into specialized versions of current classes, gaining some benifits, loosing some.

Example: Lets say in the new system gladiator has an epic +enmity skill that any DoW job can use. Unlock paladin, and switch to it, and suddenly you have an epic awesome AOE +enmity skill with half the cool down timer. BUT, you can no longer use it on other jobs.

That's the impression I got from all that.