Actually, when he first came out, his debuff didn’t work right: [SOLVED] Kingston's debuff doesn't work properly (fixed in V24)
Domitia is the one with the defense buff against holy that mirrors Kashhrek. But you have to bear in mind that the defense buff roughly doubles their defense against that color (which I’m not disputing is a huge boon). That can still be overcome partially with a stacked color. If you reduce attack by that amount, heroes start hitting softer than minions. As a Kingston owner myself, it is disappointing to know there’s a limit, but it’s probably balanced. And I don’t think we can compare that cap to increased attack, be it a rage-type mechanic like BK or Khiona, or an increased special against a certain color like Ursena, because of the way the game calculates damage. Or at least, we can’t compare it directly, because of the exponential portion.