You can still hit them with the split, it just isn't as faceroll.
You can still hit them with the split, but it just doesn't do much of anything. The piercing on it does so little that it's not really worth having on the skill, and the skill has no other interesting factors besides the piercing.
This would make it possible to buff her in other ways, and this would easily fix the problem.
Three things. First, any nerf makes it possible to buff a champion in other ways. That's kind of inherent in a serious nerf. You make a champion weak, so you have to add power back in a different place (and your nerf would be harsh enough that power would have to be added back in). This isn't a convincing argument unless you're actually proposing the more interesting changes/buffs that could accompany it.
Second, the changes on the PBE fix the problem just fine. Too much damage, too much easy poke early. Reduce both. That's a fine way to handle it.
Third, I still have problems with the design of your change. It takes a short ranged skillshot that has the only unique trait being that it can pierce for extra range, and then it makes the piercing extremely weak. Why have a mechanic that weak on a skill without other unique or interesting aspects? It's not interesting design. Your change leaves her Q in a place where using the only unique aspect is designed to be a mistake not worth doing. That's not a good change.
If we were going to go down this direction with Lissandra, just straight out deleting the piercing and reworking the skill entirely would be a much better choice. Or, we could reduce the damage for hitting someone directly, and allow the full damage on the piercing, which would allow the piercing to actually be a useful mechanic and not just an unnecessary add-on to an otherwise boring skill while also giving her a weakness to champions engaging on and trading with her.
If they can aggressively gut Kass for being the #3 champ, then they can nerf Liss less aggressively for being the #1 champ.
It wasn't a good idea to gut Kass, and this kind of Olafing is something that needs to happen less, not more. Why would hearing about how badly nerfs can destroy a champion make me thing nerfing Lissandra hard is a good thing? I'm annoyed by the Kass nerfs too, but I want it to stop happening, not just to happen to champions that I dislike.