Hi
I've seen several people mention here on the forum and elsewhere that leech feels worse/broken so I tried doing some math and will explain what may be the issue. In the 2017 version, the leech penalty was adjusted to the new weapon physical damage output. I believe the initial intention was for the new leech values to match up to what it was like previously but it does seem a little worse now. For the examples below, I'm going purely off the assumption that damage was reduced to 1/8 of what it was previously. So in the event that this isn't the case, well rip this whole post. Before moving on, most if not all wdm skills had their values modified, as part of the damage rework and possibly more so to balance skills that we're once weak or overpowered. The point is that some skills may leech even less (or slightly more) than what the leech values reflect globally.
In previous patches, leech had a penalty for each difficulty.
Pre-2017 2017
(H) 1/4 (H)1/1
(T) 1/50 (T) 1/7
(D) 1/100 (D) 1/15
The leech formula as it was explained to me is: leech = dmg * leech * (leech penalty) * drain effectiveness.
Drain effectiveness in median is isn't the same as in clod. Here it is just a value, either 0 or 1. An enemy with a drain effectiveness of 0 is immune physical damage, so basically necrobots. For this example we will only be assuming regular enemies that aren't immune so the drain effectiveness will remain a value of 1.
I'm gonna use 1000 physical damage and 50% leech with the old leech penalty for destruction and find out the amount of life stolen per hit.
Leech = 1000 * (.5) * (1/100) * 1
Leech = 5 life per hit
For the new values, I'm basing the damage off the 1/8 global damage rework. So again if this is not right, sorry.
So 1000/8 = 125 and the new leech penalty = 1/15
Leech = 125 * (.5) * (1/15) * 1
Leech = 4.16 life per hit
In the new patch, it appears leech is nearly 17% less effective than in prior patches. That may or may not sound like a lot, but as I said before, the wdm values most skills was adjusted and from what i've seen they have been reduced in most cases. So leech now steals less life and the wdm of skills is also less. With character life not being touched afaik, leech is now worse.
To give an example of one skill specifically, I'll use tantrum (YAY!)
Previously tantrum dealt 33.3% weapon damage and now it deals 20% which is almost exactly a 40% reduction to the damage of the skill. So that means that:
Pre-2017 - 1000 total damage per hit * 50% * 1/100 penalty = 5 life stolen per hit
2017 - 1000 - 40%(rounded) = (600/8) * 50% * 1/15 = 2.5 life stolen per hit
Also, The 50% reduction to knife throw on striking and arrow on striking wasn't mentioned in the change log from what I can tell. I don't know if these were the only procs affected either. Because they previously dealt 100% wdm, players could have been made aware as it significantly impacts overall damage output and leech potential.
Almost forgot. End game leech is now more difficulty to obtain in several cases. Previously with double mo bonus, A lvl 102 weapon orbed with leech to 120 could get 36%. Since its gone, and the fact that only a maximum of 5 of each orb can be cubed with an item, 5 * 4% = 20%. For shrine crafted weapons, it used to be 60% and now its 40%. This is slightly different though because shrine crafts do have the double bonus. So orbs haven't lost value here, its just that less can be added. The leech per added level requirement remained the same though. I have noticed leech % on rare/crafted helms so that kinda helps. I've also seen some on quivers, but since quivers no longer have any useful orbs available, they aren't worth using over uniques.
I hope i got most of this right and that it explains what I think is the issues players are experiencing in M2017.
/end