That's a LOT of diplomacy checks to convince enough people that the the evil dragon is poverty. But yes, much traveling all over the entire Kingdom and thousands of diplomacy checks and preaching later--yes the evil dragon is poverty now.
EDIT: Note that the dragon, which is going to have a LOT of anima, is pretty convinced that it is in fact a dragon. And there may be a transition state, in which the dragon-or-maybe-not is no longer affected by the kingdom-wide social magic preventing high-CR threats from crossing the kingdom's border. (If the dragon is poverty, well, there is already poverty inside the kingdom--so the barrier is not dragon-proof. So the barrier is not dragon proof. Uh oh.)
EDIT: More serious note, social casters will probably end up at Marshal levels of effectiveness/sucking at adventuring, for most of the same reasons. They're force multipliers, not forces in themselves. But high-level or late-stage campaigns will probably see the PCs pick up their abilities as Feats, because they're plot movers.