Eve Ult Idea (OP?)

So, my favorite champ has always been Evelynn (ever since she was released). She has gone through a number of changes, and currently she's pretty weak. The thing that most annoys me is that her ult is completely unrelated to her character. I don't know where they came up with the idea for her ult, but it makes no sense on her, so I was thinking about something that would be good for her. Keep in mind that she is not a bruiser/tank, so this ult idea is intended to help her as an ASSASSIN.

There are no numbers or anything, I just want to throw this out as an idea (a rough one at that). The rest of her skills would probably stay the same. My idea is this:

Eve's ult now removes all disables (slows, roots, stuns, knockups), and puts her in an improved stealth for 2 (up for debate) seconds. Improved stealth allows her to remain in stealth and still perform attacks or abilities. After improved stealth ends, she enters her passive stealth mode. On kill or assist, this ult will refresh and heal her for an amount (similar to her old ult).

This is intended to give her some escapability, and a little bit of sustain to help her survive in team fights. Her other skills might need to be buffed a bit because she'd be losing the damage from her current ult, and it would probably have to be made up elsewhere (unsure of this).

Let me know what you think!

EDIT: I forgot to mention something very important. "Improved Stealth" cannot be detected by wards or any true sight. That's why the 2 seconds could be debatable.