This report was prepared by the Security Studies Group at Georgetown, part of their National Security Critical Issue Task Force.
Interestingly, one of the first things they had to do was actually define, for the study purposes, just what is a "lone wolf terrorist" - as the USG and others have a myriad of definitions that don't always jive between agencies.
Also in the findings, there are some statistical nuggets worth noting (e.g., use of metadata was an aid in only 7.5% of ALL terrorism investigations, and domestic LWT is a very small subset of that. So one could argue that bulk metadata collection still hasn't proved its worth when contrasted against the civil liberties upon which it infringes (and they make this point).
Link to Final Paper (approx 58 page PDF)