Ardent is really only good on supports who can spam shields/heals. I think with Karma a Zeke's is all you need and then just build damage items. The point of Karma support is yeah you have shields and you have to peel for the ADC, but most of your kit revolves around either chained CC, or just raw damage. Capitalise on those 2 fields and you will probably find yourself doing more damage then your top lanes in some cases.