One of my players is talking about taking this spell with his Sorcerer, Arcane Trickster, but I'm not sure how the sneak attack interacts with the spell. There are a couple ways I can think to interpret it.
A.) The sneak attack is separate from the spell and it's damage isn't counted for the purposes of Fractions of Heal and Harm.
B.) The sneak attack is considered part of the spell and 25% of it's damage is turned into healing.
I'm leaning towards the first interpretation mostly for balance reasons, but I want to get other opinions first before making a ruling.