Are you sure they are noise artefacts and not compression artefacts (use of jpeg in some stage) or bit steps (use of only 8-bits tif as an intermediate or a  low dynamic range camera)? If they are noise, you might simply need a small amount of noise reduction. You should not be blurring skies. Noise reduction algorithms work far better than that. Indeed some examples might help.

Note that the sharpening has a mask slider. What you should be doing with a shot that contains sky, is to zoom to 1:1 at an edge between subject and sky and start dragging the masking slider while holding the option key. You will see the on-the-fly generated mask for the sharpening operation. Drag it until the sky is mostly black and the subject mostly white. This will make the sharpening operation not affect the sky. Then optimize the other sharpening settings. They al have equivalent effect previews while you hold option.

Lastly, why are you doing lens corrections for landscape images? I never need to do anything like that, except maybe some CA corrections. You might be much better off just keeping the image in Lightroom as the sharpening and noise reduction work much better when starting off the RAW. Then for some images that have barrel distortion that is objectionable, use the lens correction filter in Photoshop (or PTLens) after the fact. I believe DxO refuses to correct images that have been in other programs, so alternatively, if you really need the lens corrections DxO does, you could do all sharpening and noise reduction in DxO and export to 16-bit tiffs and edit those further in Lightroom.

Wow, that looks pretty bad! What kind of camera and ISO is that taken with? I see pattern noise in there (vertical stripes in the clouds mostly), which you usually don't see until very high ISOs. You shouldn't see anything like that at the camera's base ISO. You should be able to get much better results than this working with the RAW in Lightroom. If you don't mind, give us a RAW file to work with (use yousendit or a similar service) to see what numbers would work for you.