Brightwing's healing would be so broken in LoL, but if League NEEDED it, how would you balance it?

Just finished a round as Brightwing in HotS, and given that she automatically heals nearby injured allies every 4 seconds with no mana cost, I can imagine that Riot would instantly go "NOPE!" to having this in LoL. They probably wouldn't even allow it on a super-slow, super-squishy Champion, even if the healing was super-weak, due to their "no infinite sustain" policy.

But let's just pretend that Riot was adding in a Champion with this kind of auto-healing capability in (ITT, Sona doesn't count because her heal costs mana). If they had to have it, how would you want them to balance it?

#Humor the idea for this topic.