Considering the original meaning of “hit points” referring to how many shells a given ship could take before sinking, 12hp out of a basic spell is still pretty impressive.
In chainmail, the war game dnd is historically based on, a hit point is a fraction of a hit dice, each HD represents one soldier, roughly, so 12hp being the average of 4hd isn't too bad, no.
A common explanation is that there's easy ways to ward against guns. But now we're just doing Rowling's job for her. Honestly, probably better than letting her do it.