Support clerics do not get rich in NW.
You've to be lucky enough to be in the first place nation, apparently. I don't know how exactly you will earn more points per match but honestly on Seeker I get way more points than on my Psychic. Maybe the count goes like: the damage taken (without dying) together with flag captures plus a low percentage of kills, maybe attack/cast times count too. I don't know if this defines the amount of points earned, but on Psychic I kill way more than on my Seeker with few hits on LA and HA, can't tank at all plus never aims for the flag. On seeker, I cast way more skills, tank a lot of damage and aim for the flag.
Flag captures yield surprisingly a low amount of points. The most points you get are from taking and dealing damage. Seekers and BMs can get higher scores because of their aoes and tanking ability.
Pics or it didn't happen.