Stacking filters can cause ghosting and flaring especially if shooting at bright light sources.
I'd shoot the scene with the ND filter on, take it off and shoot the scene with the Grad on and then blend the 2 images in post processing.
Also, consider a little exposure compensation. A few steps down will speed up the shutter and reduce the chances of the sun blowing out.
What "more" are you looking for? What PP have you done?
I really like the first one.