After reading your post I looked him up to see what he was doing with his gear. I swapped to Holy this week due to our comp changing and we needed another healer. How viable is it to change all the Intellect gems to Spirit/combo gems? I would think more intellect would be better due to higher spell power/mana pool, but I could be wrong. Also, what haste cap are you referring to that he has? Every where I looked for 4.3 only mentions a 777 haste cap and anything after that doesn't provide an extra tick. (EJ Holy Radiance info is pre-4.3 sadly).
If it helps any right now we are doing Normal DS 10 with a Resto Shaman healer who mainly heals the raid while I was healing raid / healing tank if they took a lot out of nowhere. Been trying to play with numbers on haste -> Mastery -> crit and feel Haste is better for me but even juggling all my cooldowns I can run to about 15% mana on most fights. Though on Warmaster (did attempts this week since we had missing members) and was oom by the time he landed. One of the issues I know is the lack of replenishment sadly.