So stop tank healing so much. You're having problems with Rain of Blades, and the best way to deal with this ability is shield stacking, be it from a Paladin, Priest or even a Monk.
Here is a comparison...
http://www.worldoflogs.com/reports/r...?s=7097&e=7562
http://www.worldoflogs.com/reports/r...=10340&e=10825
He is doing similar tank healing, WAY WAY WAY more raid healing, and resultantly way more HPS. Get your Paladin to think about what he's doing wrong & how he can improve. Notice the holy power gain differences, the mana gain differences (Seal of Insight isn't even used?), spell total healing differences.
You should also ask the hunter to give spell haste, since no one else in your group can.