yea, u're right. We might have have vertex ordering issue too. Initially i tested by giving each vertex an integer id according to the order in Blender, and pass it to shader. It looks like the order is pretty close, but just a few vertices are messed up (~2-5). The rest looks ok.
My goal is to instance each object in a mesh for hardware skinning. Say, a 3D model with 2 meshes together. Each mesh has different location. By passing id to each vertex, I can move/seperate them out in shader. The reason behind this is to do reduce the draw call of many object to reduce power comsumption. Currently im drawing 20 objects with 350 vertices and 3 layer textures, it takes >15% of battery in just 5 minutes. That's too much for a live wallpaper.