Each hero character consist of 9 frames:
4f - idle; 4f - run; 1f - beinghit
The frames can have equal duration - 100ms each should work just fine.
Those are extremely simple animations; not sure if this is good enough for you.
Ofc it's good enough for my game xD,
im not planning to make a triple A title and it looks way better than the things i draw.
I'll try to upload it when its done.
Looking forward to see it! Good luck with your project!