Hi, its not really solved But i have found a work around by setting the Blog Featured Article and Blog list images to large Not ideal but it seems to work
I remeber in the Past That joomla Blog images need to be 960px wide to work accross all Tablet options and mobile devices without write many specific media device screen breaks I found it better to use a something like OchiImages or Adaptive-Images which replaces the images based on actual vistors screens sizes.
I have noticed on the Helix ultimate sites i have the issue is the same, but the setting are less noticable as the the non featured articles are using the same image as the feature article on the Estate template the images used buy the non featutred aticles is the Blog list image size which is very noticable. maybe somthing to look at?