You may not know this, but when you use raster-based effects or filters such as drop shadows, etc. in Adobe Illustrator, the default for the output of those effects is a low-res 72 dpi. When using Filters, you must change the raster settings BEFORE you apply the filter. When using Effects, you don’t have to adjust the raster settings until you’re ready to save the file for output. You can access the Document Raster Effects Settings under the Effects menu.