Domain Designer: Around 30s delay when saving a display field

[armin.lengauer]

We are having a  response time of ~ 30s in domain designer, when saving a previously updated field in display tab. The domain itself is built on around 85 derived tables and exposes around 30 Sets of around 1500 fields in total at the display tab. Though we do not experience an abnormal response time in other parts of domain designer, we face this bad response time for each single field we want to rename - and we want to rename almost all fields for data abstraction. 

According to jconsole there is no abnormality by the server in using the servers resources when the problem occurs. Also the SQL trace shows that SQL statements by Jasperserver are executed within the same millisecond and there is a gap of ~ 30s  between Jasperservers SQL requests as well. We could also exclude network latency or browser side flaws. 

Very strange - does anyone have an idea about the root cause or how to improve response times in that case ? We don't want our domain designers work with an xml editor to directly manipulate the schema.xml. 

Software configuration: 
Jaspersoft Server 6.4.3  Enterprise
MS Windows 2012 R2
MS SQL 2012