I’ll say this for maths.
I know that sometimes, there is bias, and intuition doesn’t mean anything. I’m a science kinda guy.
But I also feel like player « experience » is too quickly brushed off.
We play this game. Many of us for a looong time. Our perception must count for something.
For exemple, play 2 dozen games with an Assassin using the last tree bonus.
That’s 10% kill on skulls, and 7% kill on kills.
You’ll see some deaths. Sometimes. In fact, 10% and 7%.
Then play a while with the Holy Avenger. You should « feel » way more kills, since it’s 20%.
But not so.
It’s not science. At all. But when 100% of players using the weapon « feel » it’s not working right, and not a single player experience otherwise, it should be looked into.
Sadly, it’s a purple Ingot investment, and a not so good weapon, so very few players can try it.
If the Vorpal was on Dragon Eye, this forum would be full of crying 
Edit: also, I know fixing this sword is low priority, and I agree with that. That is why I suggested to fix the tooltip to 7%, which should take 5 seconds, and will stop leading players astray.