We were just at a site on Friday that had Picea pungens with seemingly identical symptoms.
One tree was heavily damaged on one side (client disclosed that a vine had taken over the tree and was removed last year). The vine might have contributed to a suitable environment for the pest.
Other P. pungens on the property were displaying scattered locations of discoloration, rather than concentrated such as the tree with the vine.
I must confess my mind immediately went to Rhizospaera as well, but a sample displayed no picnidia at all. In fact no signs of canker, resinosous, nothing, nada, nilch, that would suggest someting fungal. At this time of year, I would expect something to be apparent. (A sample will be going to a lab for confirmation, though.)
We did find mite eggs...
I will be interested to hear what you find out and will let you know what the lab people report back to us.