The downside of her having a full aoe kit while technically possible to hit multiple members is that she is low ranged, slow and has low base damages.
I've played liss for a long time and hit master playing her this season if that matters.
A cheat sheet for making her feel good to liss players without her breaking the game is just undoing the nerfs she received for aftershock cpot being op. So q CD, and e base damage.
She did fall behind a bit as well due to the durability buffs as her already low base damages essentially now make it impossible to solo kill anyone through sheer skill on top of the q CD nerf. All of her matchups were effected by this nerf drastically to the point where she loses matchups she should be winning or easily going even into.
Additionally in order to have a big solo presence on lissandra you are forced to opt for very glass cannon builds which are not easy to pilot, high risk and not favored in pro play due to the team oriented style of play.
She really just needs that q nerf to be reverted to be satisfying. Please.