Leech Clarity needs improved!

With the current state of Leech I find it almost impossible to predict how much healing I am going to receive, and I think that should be changed.

For example, as a blood mage I picked an ascendancy talent called Vitality Siphon which reads, "10% of Spell Damage Leeched as Life".
Having read that, I would think that if I hit a monster for 1000 damage I will heal for 100 health. That is not the case.

Firstly, depending on which spell you use, your spell may not leech any life at all. Initially I was using an Essence Drain/Contagion build and I thought it would be really cool of all of the spreading damage would help sustain my life pool. I was extremely disappointed to find out that my Damage Over Time spells would not be healing me. This is something that I would like to see change. If an enemy has 1000 hp, why does it matter if I do the 1000 damage with a damage over time spell or a "hit" spell? Either way I still have to do 1000 damage and would expect to heal for 10% of that spell damage. This becomes even more complicated when you add more effects, such as explosions or hits/spells from effigies and minions. To improve clarity for veteran players like myself as well as new players, perhaps every spell could explicitly state if it has the potential to Leech and which components of the spell will Leech. Essence drain is an example of a spell that has both a hit and a damage over time component, and it would be great if in-game it stated which components of its damage apply Leech.

Secondly, Leech Resistance should be redesigned. I understand its role. If I hit a monster for 1,000,000 damage GGG likely wouldn't want the player to heal for 100,000 hp, especially considering our hp pools don't typically go nearly that high. However, the current implementation of Leech Resistance is not a good solution. I do not have any way in game to determine how much Leech Resistance an enemy has. I do not even know which stats effect Leech Resistance. I would expect it to scale with monster level and likely rarity, but who knows? When I selected the Vitality Siphon talent, it explicitly stated that I would Leech 10% of spell damage. What is the value in including that 10% number if there is almost no circumstance where I will actually leech 10% of my damage dealt?

This lack of clarity makes it so difficult to refine my build, especially given that it changes as I level up. The amount I was leeching at level 40 is going to be different than the amount I leech at level 50 or 60 etc...
My damage and the enemy hp is going up, but am I leeching more or less each level? This healing from leech is supposed to be an important part of my suitability and my resource economy because of the additional life cost my spells have due to my ascendancy, but I cannot predict how much I will heal with any accuracy.

The problem extends to all of the nodes on the skill tree that affect leech. It is almost impossible, with the tools in-game, to predict how impactful these talents will be.

In addition to the clarity issues, Leech is unacceptably undertuned in its current state. If I hit an enemy with my biggest spell, my hardest hitting, requires multiple other spells to set up and multiple debuffs prior to the hit spell, it should move my hp bar! We're talking about hitting for 3000 damage and healing for 3 hp. If the Vitality Siphon talent tooltip was accureate it would read, "0.1% of Spell Damage Leeched as Life" and I would not have taken this ascendancy.
Not to mention the fact that due to the mandatory Sanguimancy node my spells cost from 100-300hp to cast.

Balance aside, I would really like to see changes to the way Leech works to improve clarity so that the player has a better idea of how much they will be healing when incorporating Leech into their build.

A rough idea that crossed my mind was some kind of clear minimum and maximum healing for each spell. If a comet hits the enemy for thousands of damage, can we all agree from a design standpoint that it shouldnt heal less than 5% of our max hp from leech? Also, if GGG outright never wants a spell hit to heal for more than 25% of our max hp they should say so, and state it in the tooltips in-game.

Bump - in poe1 there were leech maximums and nodes that increased those. As a chonk enjoyer there's no way to build around it rn.

Agree. I feel like a lot of numbers are put behind hidden variables that only developers know and its just very frustrating.

At this point we could have passive skills on the tree being like "should increase cold damage by a little" since nothing has any concrete correct numbers

I would love to see more numbers, even if they're behind an option in the settings. For example if I mouse over my fireball, I want to see every instance of increased fire damage, increased spell damage, more damage, etc... that contribute to its final damage.

I mean, that has to be in the game already right? When I hit something it does the math, show me the math! Please : )