In the latest version of CDW plugin for Jira (0.9.21) we implemented the feature that enables project administrators to set a default tester for each component of the administered project.
The feature works as following:
See that the tester in newly created issue was filled according to the preferences set in the project admin UI.
The feature was implemented as a solution to [JIRA-217] Add "QE lead" for component
Hope the feature will help some!