High CPU time of Finder in El Capitan
Looking at this Apple forum thread, the first solution was this:

A first guess is: bad com.apple.finder.plist file in ~/Library/Preferences/. Delete the file.

Here was another that seemed to help:

I solved this issue by setting my finder preferences for &quot;New Finder window show:&quot;  to my home folder... My issue was that it was defaulting to &quot;All My Files&quot;--- that caused finder to scan everything, images, thumbnails, etc and get up over 100% of cpu usage.