This totally surprised me with its effectiveness. Got these within my first 4 matches but it was a Friday morning so the competition was a bit limited.
Ran 4ML+2xMRM40 before, not sure why I didn't switch to this instead, because this is even more effective! I prefer the 4xLPL and 4xSRM6, 4xMPL versions, but I've been running similarly to this on a marauder, which has been great fun!
5/5, I generally have had no fun in this chassis until I tried this build. Delightful. Range is on the short side depending on map, but with a little patience, by mid game, you can just point at someone and if they happened to stand still to eat your missiles, they just die.
This has been my primary frustration with MRMs. The "stream" of missiles they put out is exceptionally difficult to use against moving targets.
MRMs in the arms are more useful due to the maneuverability, that's also why I switched to a murm stalker over, say, a mauler.