Talon has a heal when killing any unit with his Q and Ekko has an ult heal and they're laners.
Nidalee has literally always had a heal, and she was a midlaner up until Season 5.
If we go by primary class still, Master Yi has also always had a heal (which also reduces incoming damage) and he was primarily a toplane champion until Feral Flare was released. Even then, he remained a toplane champion for a good while until Sated Devourer caused him to get balanced around jungling. (and his healing was the only part of his W that hasn't actually changed since those time periods).
As for avoiding damage, we have Ekko's W's shield, Kassadin's Q's magic shield, and Fizz's E's Troll Pole.
With that list (Talon, Nidalee, Ekko, Fizz, Kassadin, & Master Yi), the primary role assassins who have been mainly laners in the past or are currently laners first, and don't have any innate sustain or way to avoid damage are... Katarina, Leblanc, and Zed. That's really not a lot, especially considering that when you add the missing jungle assassins (Shaco and Nocturne), Nocturne does have sustain and a spell shield, which puts the assassins with some kind of sustain or damage mitigation/way to avoid damage altogether at twelve out of sixteen champions, which is 3/4th's of the class.
EDIT: This didn't take Pyke into account when I wrote it, so if we add our 'support assassin' (though it's not his primary role, so ehh), this makes thirteen out of seventeen assassin champions. As Kayn's primary role is Fighter, it would be eleven out of fifteen champions if neither Pyke nor Kayn is included in the list)
One thing that made Akali in particular unique in that regard is that her healing was always among the most readily available and reliable, though, and that's something that I feel like she still deserves to keep.
