I tried to get some info from Gradle on adding Eclipse DSLD for Gradle and they scoffed at me. They said it was a multi-person, multi-year effort so why even try. I was able to get some very basic support without that much effort. It could be moved forward and probably ported to IntelliJ as well if there was some interest and support.
With regards to the change to the Groovy build script. I'm not sure newcomers are diving into the build scripts and making edits there. My intuition is that they are running "./gradlew build" or whatever the command is. As long as the scripts run successfully, I'd posit a newcomer is quite happy. I do in fact see this as at least a minor threat. If Groovy itself can't even manage to use the Gradle Groovy DSL, what hope remains for the survival of the Groovy DSL?