Why not use circle gradient particles that take the average color of the layer they are closer to, rather than using square billboards ? It might be more blurry and smoother but it would work from all angles and maintain the fully 3D volume.
By the way here’s another method for volumetric explosions that I used in Unity. It’s not the same with this technique and doesn’t have the level of detail of a pre-baked FumeFX explosion but it’s another way to do it.
It’s basically panning parallax textures on mushroomhead-like meshes with animation. It uses fresnel alpha to smooth the edges to give it a smokey look. Although it has issues with drawing order jumps since they are all translucent materials.
