Yes, using the draw event needs to draw with draw_sprite_ext if you want it to work. About the blending, it should work if you set all the parameters right.
draw_sprite_ext(x,y,sprite_index,image_index,image_xscale,image_yscale,image_angle,image_blend,image_alpha)
(that may be the wrong order, I did that from memory)
Or, if you want the simple way out, don't use the draw event for link at all. Use another object to draw the shadow underneath him.
