Heh yeah I had done it right away before we even had an idea. Our artist saw when I had (it was just a left to right wipe at this point) and said oh can you make it like erase in strips. Cue spending way more time then I planned on that effect :-p.
I agree somewhat on enemy health we really wanted to sell the erase aspect of it (its also why they linger a bit after death) and so we ran with it. I think you are right figuring out a way to have the enemies more visible would make things more readable.
All the sfxs were made with a simple wave modulator like https://sfxr.me/
Thanks for playing!