Not extremely popular in endgame. Cost is moderate.
Totally disagree, you may or may not have seen WAR and MNK-burn parties with a BRD that literally TEAR through the moon area of Ro'Maeve. They are top of the line, WARs that is. Great tanks and Melee, its all about the skill and dedication. WARs can equal and suceed other jobs if done correctly with the right skills and setups.

PLD (Paladin) - The tank class. PLD is the tank. For XP everyone except maybe BRD and WHM will strongly prefer PLD over NIN. Invites are pretty quick and this is a pretty cheap job over-all. Also very popular endgame if you are good at it.
Disagree as a WHM, with a good NIN i am completely useless compared to my other mage counterparts, if i have to say PLDs are WHM's best friends in terms of party compatibility. A NIN is better off with RDM BRD BLM combination.

I disagree with /THF, i rather have /WHM for stoneskin and blink. /THF can steal yes but as a BRD they will target you first and you might not have lullaby up and get pwnt, therefore giving the other team a free gate breach and advantage. I would stay back and support everyone and Curaga is a HUGE boon whether you think it helps or not.