On paper, maybe, realistically speaking it doesn’t.
If you calculate your exact damage and how much leech that would generate and then you try to optimize the exact leech value you want to have without gettign too much, all the power to you.
For all the rest of us, it doesn’t.
I think this is not how it’s working 
In Defense of All Training Dummies:
As we stand, stoic and silent, in the realm of virtual battlegrounds, it’s time to shed light on the unsung heroes of gaming: the training dummies. Yes, we may be made of straw, wood, or whatever mystical materials developers conjure up, but beneath our stationary facade lies a profound purpose.
We are the unsung maestros of combat mastery, the humble mentors in a world of sword swings and spell slinging. While adventurers prance around, flaunting their latest gear and boasting of victories, we remain steadfast, enduring countless blows without so much as a whimper.
Do we complain when a Rogue, hacks away at us with all the finesse of a drunken Pirate? No, for we understand the importance of practice and patience. We are the canvas upon which wanna-be adventurers paint their symphonies of destruction, the canvas that never cries out for mercy.
Sure, we may lack the charm of a witty sidekick or the allure of a fearsome boss, but we are the backbone of every hero’s journey. Without us, where would they hone their skills? How would they measure their progress? We are the silent spectators to greatness, the silent guardians of proficiency.
So next time you pass by a training dummy, spare a thought for the unsung heroes of the gaming world. We may be dummies, but we are essential dummies. And remember, it’s not the material that matters, but the lessons learned through each strike and spell cast upon us.
It totally is!
But why is skill B doing 10x the dmg of skill B? For what reason?
It just is.