Why is 9th rankup is so unfair?

[Roman_Hohotun]

I am once again struggling with the rankups... 
Oh, would you know how I "love" waiting a day because of the random mechanics...

Do I need to stealth for 30-60 minutes for enemies not to trigger?
I practiced ~10 times, managed to make it from the first try.

Repeatedly got to the 3d stage, but every time on the 3d stage 1 enemy sees a body and gets "UBER VISION" that sees you everywhere and "HYPER SENSE" that feels you if you are crouching behind him (after he returns to routine path)
On the last try I just failed, because enemy saw a body through the floor (In a place he didn't see it all the times I practiced)...
Cool...

I don't deny, that I can mess up (like sliding past enemy or failing off the map), but, why is stealth so important in a game, where you slaughter hundreds enemies with a melee?!

Or can I use regular melee here not the "stealth kill"?

P.S.
Jeez. This game just makes players to use forums or guides to get pass every challenge...

Edited 2 hours ago by Roman_Hohotun
I can't write words

[BiancaRoughfin]

First thing you need to do when moving on a stage is observe the enemy's patrol route to know where they will be when you kill, only after that should you engage.

19 minutes ago, Roman_Hohotun said:

IOr can I use regular melee here not the "stealth kill"?

As long as you can kill the enemy in one hit, it doesnt matter if you do a finisher/steal kill.

If you have any Glaive type weapon it will make this challenge much easier as you can kill enemies from a distance, just make sure you hit them and not the walls/ground as they might be alerted to it. Whirlwind Mod for increased throw range, a Zephyr with Jetstream mod or Both will make this incredibly easy.