This thread focuses on Mark of Impurity, but i am sure other skill have the same problem:

The lack of information: (german localization)
Let's have a look on the base skill Mark of Impurity:
"Mark an enemy and increase the amount of damage it gets". Well. Good. A debuff.
But - how long does it work? How many % damage does the enemy get?
These information are crucial, we need them to calculate our chars.

Thats the base skill. Now let's have a look to the modifiers.
I play like: Number= active mod, o= inactive mod

.12oo
.o34o
.5ooo
.o6oo

I can only guess what i am getting with this mods because
"1: Increase the time of mark".... by what? 0,5sec? 3sec?
"2: Deals more dmg to marked enemies" by? 500dmg? 1%? 20%?
"3: Marked enemies get 10 cursed stacks" perfect! 10 stacks, last 4sec, 100% proc chance - 10/10
"4: Deals more dmg to THE marked enemies" (german description - identical text but one of them hast an extra "den") same question... how much more dmg?
"5: Increases the critical damage at marked enemies" Yeah. Like... 1000dmg? 1%? 50% 3000% ?
"6: Marked enemies spread their mark to enemies nearby when they get killed" Good description. Nothing to complain about.

You get the idea? The lack of information makes it hard to rate the skill. Is it a crucial skill which improves my playstyle or is it just a nice to have but can easily be replaced?
Please, rethink your skill deskription