First of all, many classes are bugged on FS, in terms of damage/healing/absorbtion etc..
In this case you can't really know what truly happened. There are many improvements to healing spells. Do you know for sure that the druid used Regrowth only?? There is a chance that he repedeatly used 2 healing spells and also have good procs. What if he did Regrowth>Swiftmend?(adding the full HoTs and the healing improvements for them) or if he did Regrowth>Renewal(in this case he can't have Displacer Beast) (+having HoTs etc..) Or if he was playing the SoTF talent + Renewal. So, it would go like this: Regrowth healing increased by 200%; Renewal: heals for 30% of the caster maximum health, adding the dampening, that would be 12% of total health (+having HoTs and such)..
That guy healed for 31% (from 3% to 34%). Half of that is just from Renewal, aprroximately.
I see 1.4k's DH's here complaining about healers. Well, i know that the templates/spells/mechanics are a mess, but stay clear, the damage classes are also bugged. So, if healers are getting fixed, so should the damage classes. After healers will be optimised, don't think you ll be able to kill a healer, alone, with no dampening and being a 1.4k rated. (If Firestorm don't look a little to the dmg classes too, well.. you ll be able to kill even a decent one :thinking:).