Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Akali is supposed to have energy regen seals, but they're not on the list. I usually go with Mpen as my last Quint, but HP regen or Fortitude also works. Sell Doran's Dagger when you pick up another damage item, you just need 6 damage to activate the disc.
AP is generally preferable as it scales much better with your skills. Not sure how the new buff will affect her, I'll have to do the math sometime.