Ok, a Druid posted this yesterday (check below for photos) and you can see that I did indeed get to 2,000,000,000 in heals per second. It took two extra Priests and a Druid for the Innervate, but I'd like to explain how you Priests out there can do this. I've spent about 2 hours just exploring this exploit, and there are some things you will want to know so you can get the most out of it.
First, you need to get the Glyph of Holy Nova. This glyph reduces the GCD to 0.5 seconds, which is where all the mischief comes in.
Second, spec HOLY. You must have your mastery in the Echos of Light for this to work. It's not Holy Nova that does the healing, but the Echos that keep getting skull****ed by the super-fast Holy Novas.
Third, take your gear and reforge it, creating a rise in your mastery level. My mastery gives 18% of my direct heals into the Echo, and that helps the process grow that much more quickly.
What also seems to help tremendously is that you have at least 3 people around you when you start spamming Holy Nova. I find that the numbers jump DRAMATICALLY quickly when you are surrounded by like 10 people. If you decide to use this on Valeria Dreamwalker, you do NOT need the portals, and if you surround yourself with two to three others (Hymn of Hope and Innervate are so important) then you can heal her up in just under 30 seconds.
I also found that if I activate the Chakra for Prayer of Healing and then use the Holy Word: Serenity, it tends to boost the process in the beginning.
How this works: The Holy Nova blasts are coming pretty fast, and what the Echos are currently doing is using the previous echo plus the heal that was just done and increasing it by 18% (based on my mastery) for the next set of Echo hots. But the server can't keep everything separate, and what ends up happening is an exponential curve that has a hard cap at 2,000,000,000 per second heals.
Once the cap is hit, however, the hot RESETS. Just a bit of warning on that part.
ENJOY! I'm so proud to have accidentally made it on your boards!
Hephaestion
EDIT: Ok, I didn't read the Druids post. Unfortunately, he's completely full of crapola. He was the druid that innervated me, and there is NO need for an Abacus. Silly druid, 2Billion in Hots is for Priests.
TO REPEAT: There is NO Abacus needed, just SIMPLY the Glyph, Echos of Light and some mastery points. Innervate helps, but with a potion you can still get to 1.5 Million to 25 million heals per second just nicely. And you can sustain it for about 15 seconds given 35K mana.