Just played Akali on the PBE, here are my thoughts.
The passive is neat, I think the zone is large enough to move away, that it gives enemies time to move their distance before you can get back to them and heal from the triggered attack. In a vacuum, anyway.
I like her new Q. It's short ranged, and while the CD is a tad low at level 1 (1.5s) it's got a steep energy cost, so I think it's ok.
Then there's the W. After playing with this, everyone's fears are justified. This is busted as hell. I can basically assault any champion I want under a tower for at least 5 seconds, because all I need to do is move back into this massive cloud and suddenly the turret can't see me. This is broken BEYOND all reason, and shouldn't be in the game. Furthermore, _the duration of the cloud is extended every time you move in or move out of it._ That's fucking bonkers on something that's not even an ultimate. So what you get with this shroud is a huge zone of vision where NO enemies can see you, and then on top of that, as you do your hit and runs under the turrets, it's duration gets extended. Way to go on making a totally balanced ability there Riot. This ability will single handedly ruin mid lane mages or anyone who can't move fast enough away from her.
Then we have the E. This, too, is utterly busted. I used it, it activates the passive, while simultaneously vaulting you backwards, and then _tripping her passive's zone you have to cross for the heal attack._ Then, on top of that, you get to leap back to the target you marked, and the leap distance is astronomical, it seems as large as Kai'Sa's ultimate. This is absolutely disgusting.
**EDIT: I experimented with this more. Put a dummy just near the edge of the enemy turret in mid. Used E on the dummy. Then I used R to dash away from it, and got as far as the allied inner turret (between the outer and inhib) before I had to press E and I dashed back. It was about 2/3rd of the distance of a Sion ultimate. This shit is stupid.**
Her ultimate then, is also horrible. Her first press of the skill vaults her in a distance. It stuns enemies she vaults over for a fraction of a second, think Nautilus' passive. Then her second hit of the button launches her in a direction, dealing more damage and then dealing additional damage based on how low any enemies are, like Evelynn's ultimate.
What we have then, in the new Akali is just pure, unbridled mobility, combined with about every feature that will make her cancer to lane against, and even more cancer to kill or hell, see. This VGU looks good in terms of model, but the kit is so unbelievably busted, I cannot see ANYONE getting to play her for weeks to months because of the sheer power in it. If she has weaknesses, they're very small, and difficult to exploit.
I would beseech Riot to take this back to the drawing board. Remove this bullshit "obscuring" from her Shroud, give her a much smaller range to leap to a marked target with her E, and remove the fucking stun from her R. No assassins with this much power should be able to AOE stun, even for small times.