Make it mandatory that all pages/content be enabled with a simple satisfaction rating of that page/content.
Perhaps using the 5 star rating.
Current ACSI surveys are too bulky and limit the number of responses (13% response rates are "good"). A simple "Was the content on this page helpful?" or similar would be more effective and could be mashed-up into dashboards for measuring individual author, subsite, search engine, and navigational effectiveness.
The Agencies won't do it unless it is mandated because they are all (in my experience) deathly afraid of criticism from the outside.
As an addendum to the above, you could mandate that they accept, post, and track comments about the page itself.
This would create pressure from the citizens to the authors directly to improve their content. It is easy, cheap, can be centrally managed/implemented, and would greatly improve content over time. (publicly posted comments plus ranking)
BTW: could be moderated for threatening, perverse or abusive language as well as technology screening.
**this also would help solve other problems in the long run.