Moderator is a skirmisher, so being able to deal with heavy units and assault units is pretty much in its wheelhouse. If you need to deal with it, either use artillery or a swarm of raiders. It sounds like it's working as intended.
The only thing I could see as a change to keep it in line with its role but give raiders an easier time dealing with it
[*] is to make its weapon shoot a thin tracer line at the target for .2s-.4s before the shot fires, followed by the shot going out along the tracer line (
Example). This wouldn't affect it against riots and assaults (what it is meant to deal with), but would allow raiders the change to dodge. This might not be a bad idea for Stingers, Penetrators, and Grizzlies as well, but I don't think those units need such a change.
Optionally the tracer line could show up for a second before it stops
[*], tracking the unit during that second, as a neat visual effect.