The devs insist it's WPA vs WPA for success, and target Guild% for duration. Because why not require this much for simple support spells? And why shouldn't Paladin spells be easy? Okay, forget easy. How about easIER than offensive spells? You can more readily damage an enemy effectively than support an ally effectively, which seems backwards. Why take a personality's only meaningful bonus and make it unreasonably difficult to succeed with?