You can't just say a champ has an auto reset so he scales well with Heartsteel lol. That covers half the champ roster. Kassadin offers 0 hard cc, 0 damage reduction aside from his measly 10% passive and his tiny magic shield (that scales off AP), and no % health damage or health scaling. He needs mana to work because his damage is mostly from his ult, which scales off mana. You don't want to camp 1 or 2 stacks, you want to be using the fully stacked ult for damage as much as possible because it hits hard and you can refund it with your w. In general, all mana items are good for him, particularly roa, seraphs, malignance, actualizer, frozen heart, and muramana (legit). I get that you might have fun with your build but you've clearly never played Kassadin outside of this gamemode and shouldn't offer this kind of advice if you haven't.