Once in a while, it pays off, but it's often a huge time-waster that makes me question why I'm doing this in the first place. 
I'm hoping some may bear fruit later.
Charting them out like this give a bit more perspective. But then it's a lot of leg-work trying to figure out where they may intersect.

On my paternal line (NPE with great-grandfather), I have spent a lot of time deducing the probabilities based on shared matches and cM. I have a two main clusters on this line.
In the first cluster I've found three sets on MRCAs in the matches, and an obvious marriage between two of them. Since there is no marriage between to the other cluster I've assumed it's an NPE. All of those clusters have common matches showing the line back to c. 1725, so I can know they are solid. So my assumption is another illegitimate union between a specific man and a woman who died around 22. Best guess. All of the closer matches in this cluster also clearly have an NPE. So while we share a common ancestor, born c. 1820, I don't know who it is.
In the other cluster. It's very tricky, as all of the matches have three grandparents with the surname Jones, in Wales. Of the closest matches in that cluster, they also relate to many of the more distant ones on another line. So I need to spend a lot more time in looking into this. But the person of interest seems to be a John Jones, b.c. 1849. I need to order his marriage certificate to find out the father is, but I think it's an NPE. It's very difficult to know where that line goes back to. But the intersection and MRCAs suggest that there is an NPE with another cluster (also Jones). So I have put together a provisional tree of what I think it probably is, based on this. It's not going to be possible to know more without closer matches, either autosomal or Y.
When I got my Y test back it showed that my paternal surname was, at some point, Proctor. So this being in Wales, there were only two families named Proctor. One was 11 miles away and can probably be ruled out, as I am related to another family that married into them a generation back, so there would probably be a cluster.
The other Proctor family happened to live in the village my great-grandfather was abandoned in in 1882, where they were lords of the manor. That family had a coat of arms, which happens to be shared with my Proctor Y-DNA relatives. There's also a branch of my Y-DNA matches that breaks off c. 1100 AD where the surname is Tatham, a manor in Lancashire, where they have virtually the same coat of arms.
However, there are no trees on Ancestry with any descent from that family going back generations, as far as I can tell. So there are likely no or few tests to compare against. But that would explain why that DNA cluster appears to be blank before c. 1850.
My paternal grandmother's NPE was solved earlier this year after a closer relative was tested. So I am hoping for the same one day with this...