Use gear with many sockets. For stats, I'd go with intellect > spirit > crit > haste > mastery. With intellect flask and food, my stats were 16820 intellect, 4860 spirit, 16.86% spell haste, 17.74% crit and 53.91% mastery.
I used Horridon's last grasp and Relic of Chi-Ji (this one is itemized a bit higher than its ilvl).
Conductivity is a great mana saver there. With telluric currents, usually healing rain is enough to keep the group up (except the hunter), while in the same time helping dps with lightning bolts.
Only reasonable one is 871 for Earthliving, everything above that is waste imo. I prefer crit>spirit>mastery and use normal raid trinkets that I have, Prismatic Prison and Nazgrim's Insignia. Just happened to upload a little guide today, feel free to check it out.
nothing is really hard to heal, mana management is what matters. i used gear with the maximum number of sockets, preferring blue over all others. i ate spirit food and drank a spirit flask. my "buddies" were so slow i never got to drink after the 10-wave block, so mana regen was my priority.
The best stat for any healer at that scaled down level is INT -- it's not even close.
INT >>> spirit > crit > mastery > haste
Get as many sockets as you can and use pure INT gems.
I did some PG's on PTR long ago. Never bothered with them on live until a a few weeks back. (Got to wave 45 in like 5 tries --- was slow to SLT the enraged Conqueror!)
Knowing I'd eventually need a set for CM's and PG's, I had old gear banked.
A loose gear guide would be to catch Leeds logged in his CM Elem set and copy that as close as you can. http://eu.battle.net/wow/en/characte...siboy/advanced Just replace trinkets with Relic of Chi-Ji and another proc-based regen (Horridon's or Siegecrafter Blackfuse one are both good). You could even use the INT meta that you'd use for elem if you're comfortable with Glyph of Totemic Recall.
Mathing out scaled down haste was too complicated and wasn't sure if we get the 5% raid haste buff. So I reforged out of all haste.
Someone claiming that nothing is really hard to heal in PG's must have been very fortunate to never have chomp on the tank. I would intentionally delay using HST for just this, especially in wave 3 with double chompers. It's also why Rushing Streams is so good. Conductivity seems great on paper until the tank decides to peel an add and moves everyone out of your healing rain.
I got to wave 34 (got excited at wave 30 forgot to refill mana -_-) myself and i had the following:
I had my regular raiding build going Int>Spirit>Haste (33.something% breakpoint for HS totem)>Crit.
The glyphs i used were: Glyph of healing wave (to keep urself alive. found this worked really well), Glyph of Riptide (cleansing waters etc.), Glyph of Cleansing waters (Healing while dispelling is a great perk to have! best glyph in there!)
Talents i used: Astral shift, earthgrab totem, Totemic persistence, Ancestral swiftness, Rushing streams and Unleashed fury.
Go for pure intellect gemming always, and keep in mind the legendary meta doesnt work at all there. So buy a cheap helm and give that a regular meta gem!
Trinket wise i used the Sha of pride and siegecrafter trinket, however i heard the timeless chi ji trinket is also really good for it! Didnt test myself though.
May you have any questions feel free to send me a pm