If you're dealing with new players, BCNM's, EXP parties, and just about everything else (Blind Moby, anyone?) is wayyyyy off. The best guide for choosing your race/job is this: Look at the races, gauge their strengths, pick your challenge level, go with your interests!
In my case, I got a TON of heat for going for DRK/RDM from the very beginning. However, I KNEW that I wanted to do it. I wanted the firepower, and I wanted the magic flexibility, and I knew I'd take a hit on defense. It's not been super easy, but I knew ahead of time, and decided, as a seasoned player, that I didn't want the road to be too easy, and it's been fine. Some people want to try different combos - otherwise Vana'diel would be a lame world of clones.