RDM and SCH are support classes get over it. They were never made to be just as good healers or nukers as their respective counter parts. Their strength comes from which subs they choose and how they support the party as a whole. So youre Cure IV is weaker...you have 2 choices use a Helix to make your spell stronger, or keep Regen-ga up on party members so the WHM can focus on other buffs and supporting the tank.
As RDM you can refresh the WHM to let them use higher Cure's in quick succession while you top people off they can''t get to immediately. But this is all providing you want those job to be healers and forget their other abilities and duties. Because certain pieces of equipment give bonus if aligned with the right weather, yay for helix. SCH can also help tanks keep hate by increasing emnity gain. RDM is still the only job with Tier 2 enfeebles that can land consistently on HNMs and has an easy and simple way to change a mobs resistance with Enspells.