haven't tried out a "FULL" potency+ build of 42%, which is the maximum you can have, without a healing feather. With feather, you can have +57%.
Asklepios, Templar Mace, Aristocrat's Coat, Medicine Ring Roundel Earring (Healing Feather.
A cure V which would normally heal 800HP would do 1256 with this gear. worth a try methinks :P