1. Assume you have no public instance, or it is not reachable.
2. Start a publication workflow, and then "accept & publish" it.
3. the activation will fail, with a message in the Pulse

However, now you cannot retry or do anything with the work item. Basically, workflow will tell you that the item is already taken care of (in which case by the way it should have removed the item from the Pulse, which it did not).

That is very confusing.

The way it should be: workflow should detect that the publication was not successful and keep the workitem around. It should also tell the user that there was a problem with activation; and allow her to try again.