To quickly comment on DKs in relation to all said so far;
They start at 55 and have an incredible chain of quests to work through from 55-58, across the course of which you go from green gear to blue gear, learn your class-critical skills, receive talents points bit by bit, get your mount, and go through an incredible story.
And one of the final quests... well, I can quite simply say that it is the best quest I have ever done in the entire game. It was incredible.
Come Wrath launch, everyone's going to be jumping on the lets-make-a-DK bandwagon, and I'd heavily recommend steering clear for a while; maybe wait a few weeks or a month, enjoy levelling your main. Given time, the huge number of DKs will wither down to a smaller number as people realise that they either can't do stuff because there are too many of them, or drop it because they don't find it as entertaining as one of the other classes.
And as for professions... well, I'd leave it till 80; simple fact is, it takes ages to grind them up to an appropriate level, and it'd be better if you save it till you're sitting pretty at 80, by which time the realm economy should have stabilised and it'll be easier to get what you need to skillup rapidly.