F YEAH, that patch moves all vertex calculations to the shader.

https://github.com/pixijs/pixi-spine/blob/gpupatch/gpupatch/SkinnedMeshPatch.js

Some shader code:

void main(void){,
   vec2 ffd[4];
   ffd[0] = aFfd11.xy * ffdAlpha[0] + aFfd21.xy * ffdAlpha[1] + aFfd31.xy * ffdAlpha[2] + aFfd41.xy * ffdAlpha[3];
   ffd[1] = aFfd11.zw * ffdAlpha[0] + aFfd21.zw * ffdAlpha[1] + aFfd31.zw * ffdAlpha[2] + aFfd41.zw * ffdAlpha[3];
   ffd[2] = aFfd12.xy * ffdAlpha[0] + aFfd22.xy * ffdAlpha[1] + aFfd32.xy * ffdAlpha[2] + aFfd42.xy * ffdAlpha[3];
   ffd[3] = aFfd12.zw * ffdAlpha[0] + aFfd22.zw * ffdAlpha[1] + aFfd32.zw * ffdAlpha[2] + aFfd42.zw * ffdAlpha[3];
   vec3 skinned = vec3( 0 );
   skinned += boneGlobalMatrices[ int(aSkin0[0]) ] * vec3(aSkin0[1] + ffd[0].x, aSkin0[2] + ffd[0].y, 1.0) * aSkin0[3]; 
   skinned += boneGlobalMatrices[ int(aSkin1[0]) ] * vec3(aSkin1[1] + ffd[1].x, aSkin1[2] + ffd[1].y, 1.0) * aSkin1[3]; 
   skinned += boneGlobalMatrices[ int(aSkin2[0]) ] * vec3(aSkin2[1] + ffd[2].x, aSkin2[2] + ffd[2].y, 1.0) * aSkin2[3]; 
   skinned += boneGlobalMatrices[ int(aSkin3[0]) ] * vec3(aSkin3[1] + ffd[3].x, aSkin3[2] + ffd[3].y, 1.0) * aSkin3[3]; 
   gl_Position = vec4(projectionMatrix * skinned, 1.0);
   vTextureCoord = aTextureCoord;
}

I opened a game that uses a lot of spine animations, pasted it into console and got 60 FPS instead of 30.

You can try to port it in other runtimes, I've noticed that people are complaining about performance in Unity.

There're no benchmarks yet, but I'll make them soon.

P.S. Is there anyway to get a discount on spine prof. version just because I'm awesome?