Tough one to deal with here, as it can be many items. The LDAppVulnerability pool also handles software distribution now. Normally if it is a DB issue you will see high CPU on the core side. How often are you running vulscans and checking for new policies? Also are all your pool settings the default (besides worker processes)? I would try these:
- Check you IIS logs for errors 503 on vulcore.asmx.
- Check SQL logs for errors
- Run coredbutil - Build components.
- Check DB Table sizes http://www.planet-source-code.com/vb/scripts/ShowCode.asp?txtCodeId=732&lngWId=5
- Defrag SQL DB http://community.landesk.com/support/docs/DOC-2407