I have had the same out of memory problem too, which for me is a deal breaker. I have shyed away from using the report tool out of ArcGIS for Desktop for this main reason. And now that Pro is out, there isn't any way to do reports at all.
What software do you then use for your report needs?
I use MS Access to create my reports with. I can tie directly to SQL using an ODBC DSN, which allows me to get to the feature classes and attachments tables. I had to utilize both linked tables and a make table query in order to get the relationships I needed in order to create the reports (the relationships do not come through in Access as they do in ArcMap). It isn't as easy as what ESRI has built in, but like I said the whole memory issue is what drove me to find something different. I am hoping to talk to the developers at the ESRI UC this July to see if I can pick their brains a bit more on an easier solution. But for now, at least I have what I needed, and I suppose I could use it for other reporting needs, but not sure if it is worth the time and effort.