Its surprising minor characters are often amusing with a distinct voice. Momodi (uldah starter npc) is one of these.
The problem with the main plot npc's lies in the fact that they are members of the circle of knowing -
a) they know too much already. Contrast this to other FF's where most good guys were just as much in the dark as the player and events unfolded and we had all those "ah ha / so thats why x happened" moments
b) they all appear to be level 99 already. see r46 mission, we as players have no desire to cheer them on, theres nothing at stake as they have always been "uber" since mission 1. Contrast this to other FF's where allies got their asses handed to them and so we watched the characters grow and develop into the finale.
c) its boring that the npcs all come from the same group (circle of knowing). Contrast this to COP where all the allies came from different parts of the world and different factions with different world views and motivations (Shikaree sisters / Louverance / Tenzen / Prishe / Selteus / et al - the in game lore practically doubled as all these characters and mention of other regions was introduced).
d) as a result, Yda, Papalymo, Thancred, Yshtola have all taken on the role of the same character within the story. Fair enough if the stories were nation specific, but as they merged that was a no no. It would be like watching star wars and every ally was obi wan.
e) we know practically nothing about them, we dont have any quest lines to find out their background. we have the Echo but dont think "hold on a minute lets find out who these people are lol". contrast this to any other FF. my favourite parts of other ff's have often been the sidequests finding out a characters past and secrets
And the Path of The Twelve lady has to be the blandest NPC in any RPG. She doesnt even have a unique model. Further the whole concept of the Path of the Twelve with all their rules make the whole concept of the Echo seem dull. Whats the point of having such a power if we cant abuse it. What is the point of this faction? It seems wholly unncessary.