I needed a break from my item compendium, so I started looking at Empathy.

I haven't broken the formula, but I've found some things that made it significantly easier to reverse engineer.

Here's what I found:

* Empathy, rank 6, always has a spread of 6. The description says it "heals for 30-35", which is an average of 32.5. Even when it scales, it's always a spread of 6. 45-50! 52-57! 56-61! Because of this, it was very easy to test weapons.

Just get a weapon, start getting hit, cast Empathy, and keep doing this until you get a spread of 6. Record your min/max heals and your str/dex/int/min dam/max dam/weapon stats. No averaging or keeping track of individual samples is needed.

* Assuming the description is correct, Empathy's formula is:

<AVG EMPATHY HEAL TICK> = <BASE EMPATHY AVG> + <SOME UNKNOWN QTY>

* Increasing your overall min/max damage by 1 for the same weapons increased your healing by 1. I only tested Rifles and unarmed, though.

* It looks like item level in addition to min/max damage contributes. If I matched up min damage or max damage values, my lv18 rare rifle always healed for less than my lv 20 common rifle. Likewise, my lv 15 common rifle didn't fit on the healing curve of my lv 20 rifle either. If it were just min/max/avg damage, I should've hit the curve.

However... I did have a lv 19 common rifle with almost exactly the same stats as my lv 20 rifle (+1 min/max dam). When I used it, I WAS able to hit the curve.

Here is my data:

https://docs.google.com/spreadsheet/...=1&output=html

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That's all the research I can do for the next couple of days. I hope I've planted the seed of curiosity. It should be very easy to track Empathy, given what I found out about fixed spreads.

Things to try:
Do different weapon types have different curves?
Does the damage implant increases your empathy ticks by 5?

Figuring out how Empathy works is critical for us to understand how skills work in general. I bet Leech, Wither, and Transference all have fixed damage spreads.