YOU NEED TO DOWNLOAD THIS TEXTURE OTHERWISE THE WA WON'T LOOK LIKE THIS: https://www.dropbox.com/s/80us14fa05sz9kj/shooting_stars.blp?dl=0
Once you download it, move it to Interface>Addons>Weakauras>Media>Textures
The same texture is used in retail for virtually the same effect (instant Starfire)