MNK and DRK are both excellent jobs. Id say lvl you WAR to 30 grab DRK and lvl both MNK and DRK to 30 and see which you prefer, or stop if you cant stand one =P.
Im a 41MNK on Siren and i love it, we might not hit as hard per shot as a DRK but DOT, as you can view in the MNK boards, a well equipped MNK can outdamage a DRK.
Though DRKs are still a incredibly useful and powerful job. the Absorb-Stat line of spells are incredibly useful in xp pts for weakening up the mobs when doubled with blm spell debuffs for stats and the dmg is nice.
Our servers overpopulated with DRKs and some ppl dont seem to like MNKs all that much, but that just means either way ya gotta go all out ^^