The problem is that Ana doesn’t have lower self healing. She has none at all.
Using the grenade doesn’t qualify as “self healing” as it’s being defined in this context: healing yourself without the use of activated abilities.
Ana’s lugging around a gun full of healing darts, why not give her a passive that heals her when she reloads? For every dart left in the clip, she gets a point of healing. This preserves her weakness of having low self-healing, but it lets her recover when she’s out of combat.
Brigitte and Lucio are close-range brawling heroes. Ana was intended to be a long-range healer. If Ana is playing in her intended range and she gets jumped, even if Brigitte/Lucio successfully peel for her she is almost always be forced to use her grenade during/after the scuffle, so she recover in time to get back to doing her job.
Ana needs a way to recover without using her grenade sefishly.