@evouga The issue with Kambal is that while his drain effect is more powerful, the colors that he is in lack reach. I was literally running OG Kaya in a Kambal control list (metagamed against PO and Blue Cantrips) in part because I found the drain effect to be synergistic and won several games with Kambal holding back Pyromancer tokens while Kaya drained the opponent.
Cinderlash is a less powerful drain effect but it is a harder to remove permanent for most decks and in the same colors as Lightning Bolt. I honestly don't think the card is insane against PO, but against previous versions of Blue Cantrips, I've run Snapcaster + Fiery Confluence as a win condition. I think you are underestimating how drawn out those games can be and how the life loss from Phyrexian Mana, Force of Wills, and Fetchlands can add up.
I don't like the card against Shops, Eldrazi, or Survival, but it's not dead there. I think you forgot to mention that you can pick off Hollow Ones out of survival. But while you are listing reasons why you consider the card to be unplayable, to me it's mostly just what I would consider metagaming. I would only play this in a heavy blue metagame. Probably one with Oath as well.
Card evaluation and brewing is mostly about identifying decks in which a card's potential is maximized and a metagame in which a card a card's effect is desirable. That might not be none of the current decks or the current metagame. So it goes.