Why are there no multi-hit skills on Sage?

[Absurdity]

The only problem I can see is that if it’s a DPS loss it goes down the route of ShB lilies, if it’s neutral it just ends up like pneuma where it’s functionally an oGCD or if it’s a gain then the heal stops being important

I wouldn't even mind if it's another DPS neutral skill as long as it interacts with Kardia in a way that allows you to alter it's functions, for some synergy in your kit.

As an example let's say it's a 5 second channel (so it's 2 GCDs at 0 spell speed), dealing (as of right now) 660 potency but procs a Kardia heal every second, allowing you to buff it with Soteria or make it a party-wide heal with our new oGCD that spreads Kardion to the entire party.