RDM and BLU are both flexible and powerful in Chains of Promathia (RDM don't really hit its stride until AFTER Promyvion-Holla/Dem/Mea, however).
SMN and WHM are MVPs in almost all Chains of Promathia missions that don't involve horrendously fast damage (Snoll Tzar, I'm looking at you).
BRD is good in nearly every fight except for Diabolos and the early Promyvions.
NIN and PLD are of course useful as tanks in virtually every battle.
With all that said, no job is good if you hate levelling it.
However, hopefully at least one of the above jobs appeals to you enough to merit spending some time on it to make your life easier in CoP.
Icemage