OK I'm gonna have to reiterate what already said with more emphasis.
again, look at metal slug to understand
Look at this one.
http://laurelyn.folio.free.fr/Pixi/Steam/METAL%20SLUG/Anims/fio/028.gifsee how the eyes are placed diagonally to her mouth at the middle of the animation? that shows they were willing to break the model a bit to make things lively, this is why squashy cartoony styles are good for this.
http://img3.wikia.nocookie.net/__cb20111129203504/metalslug/images/e/e0/Darkmetalslug.gifThis is a fucking tank, it's made out of solid plates of metal and yet it wobbles around a whole lot, this is the kind of style that works with subpixel animation.
http://img4.wikia.nocookie.net/__cb20081231133745/metalslug/images/c/c9/Mv280b.gifmetal too. look how it twists around, that's the point. See the rocket launchers changing shading? that's the other thing that goes GREAT with subpixel and the other thing besides off model wobbling that makes it shine. make it a chance to show that you're constantly thinking of the light source in every little movement.
it is a great opportunity to tweak the shading, so it works great with shiny things with hilights and speculars.
http://img3.wikia.nocookie.net/__cb20081231135142/metalslug/images/2/20/Sarubia.gifLook at the way this wobbles BETWEEN shooting. look at the little cranes in the treads. See how all sorts of little highlights and shadows move around? that's most of the appeal of subpixel animation, giving a greater sense of volume and realism by showing how even the slightest movements changes the way an object is hit by it's lightsource.
NOW, I'm not saying go and do a bunch of wobbly off model stuff for no reason whatsoever, that's why I mention PURPOSE. subpixel has absolutely no place in the middle of an attack, you're supposed to be speeding up there not slowing down. you could use it at the beggining to build up or at the end for the follow trough, for a showy pose that you want to freeze time for.
a cartoony movement with slow squash/stretch, slow weight shifting or a showy freeze time pose, a shiny object rotating and changing shading, an ilde animation with with a lot of wobbling or vibration are all good times to do it.
I'm gonna be honest here, I think this is one of those things that we made out to be a technique when we were starting pixelation but really it's barely so. Mostly it's just about tweaking things a LITTLE bit without even changing the silouethe of a sprite and make it seem like they moved, hence the emphasis on changing shading. You know how often you drag and drop a face from one place to another to animate it? this is a fancy name for changing one or two things on the hair to not be cheap and just leave it exactly like it was. rotating stuff, too.
check the hood of this chick I drew. those pixels that change a little bit.
the hair and hands on this one. how the front part of the hair hanging on her back puffs out first and then the back part. all the rotation in her hands.
To be honest most of the time subpixel animation is really of no use at all. if you're trying to put badges on your belt to be a better animator you probably dont need it for a long time because your style really doesnt lend towards it. You tend to do very in model stuff and also you tend to do stuff with celshading so really it's not gonna shine very much in your animation. maybe with hair/capes/shiny stuff rotating but not much.
Right now I think you're better off learning more about anticipation and follow trough, that is the very soul of anime and you could do with knowing how to pace your animations better (who wouldnt, really? :p). Look at your favorite anime. Look at Sean Leslie Ward of Hyper Light Drifter
Sorry if this seems a little harsh but with the last sprite I thought your application of this was actively making things worse, you clearly have a hang of what this is and roughly how to do it but I think your application is not very purposeful, until you get that part it wont really be something that draws people into your animations