Don't know akali, so I won't comment on her.
Darius, Fiora (without lifesteal on items), Illaoi, Irelia, Xin, Vladimir(?), it's not drain tanking. Their healing is independent of the damage they deal, which means it's possible to tune both damage and healing separately, and you don't have the core issue of drain tanking, that is if you are ahead, you build more damage, kill more people AND are unkillable because you ALSO boosted your healing by building damage.
Olaf, Nasus and Warwick are actually drain tanks, but Nasus his kept in check by his need to stack, and Warwick is currently reworked. That leaves only Olaf, which isn't so many champions that it's a convincing proof.
Riven isn't a Drain Tank, but she does have a shield scaling with AD, so it's a related issue, even if not exactly the same. But the fact it's a shield and not a heal makes it less of a problem, by far. You need to time it right, etc.
Graves and every ADC lategame, well, ADC are supposed to be the dominant class lategame, and they need to work to reach this state. Plus, they are so squishy that they can't 1v5 like Nasus or Olaf or Aatrox if he was buffed.
Kled, I don't understand what your referring to... His AD scaling shield on ult? That's kinda ridiculous, absolutely nothing to do with drain tanking...
EDIT: I checked for Vlad, most of his healing scales with AP/damage, but he was reworked recently precisely to make sure he was healthier than before. So I should have put him in the same category as Warwick, not with Darius and co., but it's still not a convincing proof.