When Workflow application is republished, it will not retain its previous Application Pool. This may be problematic when specific Application Pool is desired for security, separation or performance reasons.
Design change in Workflow 7.6. After reviewing the behaviour, it was decided to change this back to previous way.
This issue has been fixed in Workflow 7.6 Rollup (build 7.6.4383.496 and newer). See INFO2509 for a list of fixed issues in Rollup. To acquire the roll-up please contact Symantec Technical Support and reference this article or the Rollup article.
A workaround exists in the form of clearing out the App Pool Id field in Deployment Info settings.