As you already know, to have a complete set we need to go through about 550 monster sprites to animate. That's a *lot*. We needed a way to get through them (relatively) fast. One of our methods to speed things up is using a single animation set for all monsters with similar anatomy. For example all humanoids share the same basic animation set. That way we still have to prepare 550 sprites, but we don't have to invent 550 individual animations. (The system can be easily extended, so although this is a good starting point it doesn't mean we won't customize the animations further down the line).
We also try to make the animations minimalistic at this stage - so no fancy extra frames, no unnecessary elements, limbs, etc.
This is all well and good, but every once in a while we run into a monster that just doesn't work well within these limitations.
We've had some good honest feedback back in February about the early animation attempts. Just a quick recap of the animation gif that post contained: