Its not fair. I believe its broken. As almost anything in this game.
Million times i had assassin already pouncing someone when info sound for him only starting playing. You should tweak spawn points or add delay as to gas rat.
His jump speed is random. If he jumps from the fence/ground he can turn into FFFFFFFNG super sonic and catch you on 1/3 distance of your dodge. If he jumping on you from upper edge close to you, he will fly in slow-mo so you can grenade him if you want.
His “vanish” animation makes no sense. He jumps, misses, getting hit from grudge/blunderbuss, starts smoke bomb animation only to attack you from very same spot with delay of 0.2 sec again.