Although we started using TeamPulse is same way you are now, we found the same unpleasant consequence where the current ownership of stories would we be with the last QA that worked with the story and marked it as done. As a a result, we ended up assigning the story to the development lead that has responsibility for it and creating tasks for any work related to the story, including QA work.
So for example, a story that is assigned to a developer will have a task to create the acceptance criteria (assigned to a QA user) and also a task for reviewing (done by a dev peer), and testing the story (done by a QA user). With this approach, the overall responsibility for getting the story done on time remains with the development lead and all of the other players involved, including QA, have tasks that can be assigned to them and worked against.
All the best,
the Telerik team