My critique: This animation is pretty close to terrible.
1. The eye blinks are ok. There is something hinky about them that I haven't yet identified, but I already know that something as simple as an eye blink will require tweaking.
2. When SN (soft ninja) looks to his left his eyes stay the same width apart. When I was animating this I didn't think it was a big deal, but the more I watch it, the more I think the eyes should get closer together the closer to either side they get.
With SN I have intentionally created a character with very few facial features (no retinas/pupils, no nose, no mouth and no hair). This is great for speed of drawing, but it makes facial expression a challenge. I tend to cheat and use the top of his mask to simulate eyebrows and the bottom his mouth. Because of his limited features I need the few expressions he can do to be perfect.
3. I like the puzzled/angry expression he makes when he is looking to the left. His mask makes a V shape like angry eyebrows. However, I found moving this expression to the other side of his face to be almost impossible. That will take some thought.
4. When he looks right he squints like he's incredulous or thinking hard. That's ok, but when his expression relaxes and moves back to the center his eyes are too angular.
Anime Studio is a vector based program so basically you are moving points around. Based on these points the program determines how your line will look. A simple circle only requires 4 points. But if you want to squash and stretch that circle you're going to need more points. The more points you have the more difficult it is to animate your object and the longer it will take to render your scene. The fewer points you have the less likely you will be to emulate the smooth flow of cel/hand drawn animation.
The good news about the first animation I have posted is it is not the worst I have ever seen. Also, I have set the bar pretty low. It should be easy to improve from here.