If you compare Lissandra damages output to other mages, you'll notice that her damage output is very low to other mages,
the fact that she has a suicidal playstyle require her to go in and ditch out her whole combo while trying to rotate as much Qs into it.
Another thing to notice, alot of the mages that runs aftershocks are short to mid range mages, requiring to be fighting classes like Bruisers, Fighters, Tanks.
On top of their low base hp and armor and mr, aftershock is an ideal runes for them vs high damages champions that require all in.
What are the solutions I propose:
Nerf aftershock on ranged,
buff the champions that require aftershocks,
Bring back their base damage in par with other mages,
buff their base hp and base armor and Mr.
They are Short-Mid ranges battlemages, they need some sort of increase in base defense.