While I agree that E is meaningless, your spell-vamp on E is only 33% due to being AoE, so you need to hit minimum 4 targets to get the full effect of spell vamp out of it. Yes, it's not 'hard' to get 4 targets hit, but it also doesn't do a lot of damage, so couple minimal damage with 33% spellvamp and you don't get a huge return in terms of spell vamp, her Q and R are what really give her the spell vamp sustain.
Her E is her only wave clear, but it's quite pathetic at best unless you're insanely ahead. or you're going AD Akali (lol)
If you're jungling Akali, that's a whole different thing entirely, as she was designed (I think) for being a laner and that's what I'm basing everything off of, I do not consider jungle Akali to be even note worthy. That is just my opinion.
And I've thought about her E being replaced by something similar to an enhanced auto, but that's just another binary mechanic. It basically has 1 use, out put more damage. However, if you change it similar to Vi's E (cone of damage) then you add a little bit of intricacy in the form of positioning. Which again, isn't all that interesting.
They should really put her passive into her kit more, by this I mean she has twin kamas, make her E switch between kamas (a passive or active on her spells based on which kama she has toggled) or something similar to that. It would add something unique as well as make you decided on which kama is best for which situation, along with removing the point and click nature of her kit and replacing that with a skill shot or 2.
As for her W, I find it pretty lack luster at best, it's an invisibility ability that's confined to a small bubble, so if you don't see her, she's in her shroud, thus you know her general where-abouts, but I find it especially useless come mid-late game, as vision trinkets cost 250 gold now, so everyone has one by the time team fights roll around. So you're shroud essentially turns into a vision trinket waster instead of actually being useful.