Recently I also have the issue of Sigma 18-35mm lens cannot produce sharp image with my Canon 70D. I also try to perform the micro adjustment in the camera itself but still not very happy with the result might be due to the camera micro adjustment only have two setting per lens (W or T) therefore in some situation the output picture still not sharp enough. Until I purchased the Sigma USB dock to perform the micro adjustment now i am happy with the output for the lens
The USB dock allow you to adjust your lens with different focus length (if your lens is a zoom lens) and also based on the object distance away from the camera. You can see the image below showing the before (top portion) and after (bottom portion) effect of the fine tuning.
I had attached two jpg file, one is the before & after of the fine tune result and the other is the fine tune setting using the Sigma application with the USB dock. You can see the difference between the before and after fine tune really have a lot of difference in term of its sharpness. Hope this will help those who face the same issue as me.