Does Akali need all that spellvamp?
If I look at the list of extreme mobility/burst assassins, I see a lot of things in common. They all have abilities that allow them to engage hard on a single target, and abilities that allow them a chance to get out afterward. What I dont see on most of them is the ability to regain a quarter of their HP instantly by spellvamping from 2 abilities... Once she gets some damage, Akali vamps better than freaking 
What is it about Akali in particular that justifies not only massive burst, but vamping back huge chunks of HP at the same time? Isnt Akali's defensive tool supposed to be the shroud? Just imagine if
got backa quarter of his HP when he hits you for 2/3 of yours.. Fizz is just as vulnerable to being blown up if his E is on cooldown as Akali is when she cant use her shroud, why does Akali get another layer of defense in her kit?