Usability for site builders and site administrators

Site building & case studies
Experience level: 

The administration interface should allow users to build sites ranging form simple storefronts to ambitious digital experiences - but currently it's not up to the job.
Usability improvements often focus on introducing exciting new modules, or on making the UI less confusing for new users - but there is also lot of room to improve the usability for the site builders and advanced administrators.

I'll give concrete examples of bad usability for site builders - and some of the underlying reasons - and then discuss how we can improve the User interface for core and contrib modules.
How can we decide on UI standards, without getting lost in a bikeshed conversation? How can we write them so any developer can easily follow them?

This session builds on previous sessions at DevDays2016 and DrupalCon Dublin.