I'm so glad someone else has seen this. I figured I was going crazy. I saw this for the first time on Gruul last week and when I said something in the paladin channel, they were all totally confused at what I was reporting.
I didn't have Quick Recovery, but I did have amp magic. My group has a warrior, rogue, rogue, rogue, enhancement shm. Sometimes I'd be getting the usual 95 point heals, but then it would seemingly randomly spike up into the 300s.
At first we just thought it was a UI hiccup, but I turned on combat logging and there in the logs you'd see things like:
3/27 22:42:57.946 Your Seal of Light heals you for 95.
......
3/27 22:43:01.952 Your Seal of Light heals you for 313.
If you want to see the whole combatlog or parse it for yourself, it's sitting at
http://www.ironyguild.com/raidstats/gruul_032707_1.zip but after looking it over, there weren't any anomalies that I could see.
More than tripling the amount healed puts it out of the range of SoL somehow critting, and the pallies in question weren't changing out their healing gear mid-fight, so I'm kind of left without a clue on this one.