I know the consumer submission gets an immediate reply but I am unfamiliar with what happens with corporate. I have stirred up 2 lab techs hopefully 1 is online to answer this.
As he states in his response, Every file we do not know is "suspicious" until it proves it is good. Without samples I cannot not submit anything to the Antimalware Team for review. Since on version 184.108.40.206 I was not able to reproduce the issue with the nsis installer, I believe that this might be an issue with the engine itself. At this point I would recommend that you file service requests with the files that need to be reviewed.
What the owners of NSIS need to do is apply for their software to be cleared and then maybe everything else using it would automatically be cleared as a result.
It would appear that the software may have changed, hence they would need to re-apply.