This is fascinating and currently inexplicable.
I am not aware of any thread priority changes in 2.0. You may be able to find out the priority of the application thread using Hotspot's JMX mbeans.
I don't think that the applications shipped with dm Server are likely to contend for CPU when they are not in use. You could check by deleting these applications from the pickup directory and see if that improves your application's performance.
If you can package up a simple example of this problem, say a single binary bundle that does socket IO, we could look into it further with a profiler. Or you may like to try that yourself. We have successfully used YourKit in the past, but many such tools are available.