Screenshot rot is a persistent misery for all content production, and it will remain so until we fundamentally automate how we obtain and reference screenshots (tools such as Dr.Explain are trying). It's tempting to avoid screenshot use to escape the work of keeping them current, but that doesn't serve our visual learners.
For screenshot maintenance across most documentation and training, the first defense is simple reuse. When using Microsoft Office instead of a content management system, I dynamically link (Insert | Picture | Insert and Link) to the same screenshot files used in the documentation, so that updating one screenshot updates it in both deliverables. Years ago, I created a production process that built Powerpoint files directly from Word-based documentation source, using some VBA magic -- the results were limited, but the set of training presentations were always as current as the latest build.
Annotated screenshots are harder. I store annotated screenshots in my tool's native format so that it's easy to swap out the underlying bitmaps. A trick I've used in the past is to source annotated screenshots and diagrams in Visio, then use its Publish to Web feature to regenerate the set of PNG files that I can link into documentation and training. As long as the number and order of the Visio sheets in a given file do not change, the filenames that I linked to remain constant.
For release QA, I always try to automate whatever kind of "diff" batch processes I can. Sometimes comparing code files or tests can identify where UI elements have changed across versions, so at least there's a checklist I can manage and follow for the updates I need to make for the release.
However, I'm now facing a new problem: how to single-source and maintain presentation content in the cloud. We use Google Apps for Business, not Microsoft Office, but training materials are still being created in Powerpoint (by those who have it installed) and stored privately, which defeats so much of the strategy (that all staff can search, copy, use slides).
I also need a good system for single-sourcing cloud-based diagrams that go into these presentations, but even Google doesn't make it easy to put shared Google drawings/diagrams into its own presentations. So, I'm currently sourcing in Powerpoint (which has the richest feature set) and importing into Google Presentations as the internally "published" version, but I don't see a way to automate this. Bleh.
Holler if you have any brainstorms for new ways to manage training graphics! For example, does Prezi play well with external content? do any online diagramming tools (such as LucidChart) double as credible presentation tools?