Don't adjust any of her numbers. Don't change her overall kit. Just change one aspect of her play, a simple aspect. An aspect that actually makes sense in the context of the other units that share a similar "feature".
It breaks or is delayed if she takes damage, going into it, or already in it, just like Twitch and Eve. The moment she steps out of the shroud, she is visible. Not this 0.5 second delay **** that lets her step out and be 300 units away before she is seen.
Not only is her current stealth mechanic out of sync with the other assassin champions, but it doesn't actually require skill to use, like the others. At least with Eve and Twitch you have to be mindful of your steps, timing of use, and overall placement. Not with Akali, drop a shroud and troll face. Did that Akali player make a mistake and step out of shroud? Doesn't matter, still stealth!
Akali's stealth is broken, out of sync with the others, and simply too damn easy to use. She is a super high burst assassin, and should be, but her big play should require some sort of thinking and skill. It doesn't require any of that right now.
Her damage is fine, her mobility, psssh, fine. The instant stealth that can't be broken, is too much.
inb4: Pink, Oracles, blah blah blah. It isn't about that, it is about a mechanic of a champion that doesn't fit.