Ok, so nobody seems to be asking:
Why is WHM's status as the premium healer so sacred that nobody seems to question its ubiquity in parties? It seems to be this big issue with people that jobs like BST, SCH, GEO, and BLU have become staples to parties. If a RDM or SCH, WHM's closest relatives, were tasked with healing damage and status in some of the hardest battles these days, they simply couldn't compare.