Noticing that no matter how much healing power you may have, the healing turret will only ever grant 130 health per second. Right now I should be providing just over 272.
Info from my current tooltip:
Regen(8s): 2,179 Heal * 2,179/8=272.375 HP/Second *
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Interestingly, the number 130 does match up with the following scenario:
1) Level 80
2) No points of healing power
3) No points of Boon duration increase
The raw tooltip is as follows:
Regen(8s): 1,040 Heal * 1,040/8=130 HP/Second *
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Also, for some reason, Regen will sometimes suddenly drop to only 5 HP/second. Often with neatly fatal results. Others have stated this seems to be related to the turret being destroyed. I have not tested that personally.