About the post itself, I think there are more than just smoke effects that make it sakuga-worthy. The multi-layer fire particles (which as far as I can tell are hand-drawn) add depth to the scene. Some CG elements are cleverly switched to hand-drawn animation when close to the camera (e.g. Armin's broken face and Eren's forearm at the end before he swings it down), not to mention lots of the CG is already completely drawn over with smears added.