"Why are you playing Akali mid lane?"

While we're fixing champs I'd like to not have to build full tank on Eve every game just to survive long enough to squeeze out some below average damage

She can barely survive mid before 6. Then gets camped hardcore. I remember when someone (Voyboy?) picked her vs Yasuo during Worlds some years ago - Yasuo had exhaust and his jungler was nonstop mid. Akali is super unreliable - at least top she gets some farm.

Because that's what she's meant to be?

Akali was released before mid-lane assassins were really even a thing. Fizz was released latter than her and was widely considered a sub-par top-lane champion. The only assassin that was really considered a mid-lane pick when Akali was released Kassadin due to his extremely obvious anti-mage kit, mid-lane being a good place to send Assassins wasn't really embraced by the meta until season 3/the tail end of season 2.

So: not sure I'd say Akali was meant to be played mid lane.

Also: Riot's nerfs to Akali have turned her into a fighter for all intents and purposes at the moment.

Big difference between fighter/assassins like Irelia and Jax vs. actual assassins like Zed and Fizz is largely in how useful mobility and speed are in surviving long enough to do work. In the case of Jax and Irelia: speed lets them dive on a target, but then they require ~6 seconds to kill something with a heavy reliance on solid sustained DPS. Both champions are largely stuck next to wherever they dashed, preventing them from really utilizing mobility to dance around their targets and be a slippery foe. In the case of Zed and Fizz: both have really impressive mobility in-combat that allows them to actually rely exclusively on speed as their primary defensive option, allowing the pursuit of glass-cannon builds. In both cases: the champions have really swift combos that don't mire them next to an opponent, and they both have a get-out plan.

Akali is more in the dash-in and get stuck phase with sustained-DPS ATM, much like Irelia and Jax. Akali's Q mark got nerffed so only an AA detonates it, and Akali's stealth activation took a sizable hit so now there's a noteworthy delay before slinking into the shadows.

Akali's current play-style and optimal build-path is that of a fighter, which is why she's being played as a fighter. As an assassin she was sitting in the bottom rungs of win-rate charts, as a fighter she's seen noticeable improvements in performance.