Targets such as Atlases will always be hit by non-locked LRMs even at ranges of 750 meters, unless they're fast Atlases which do not exist in some meta (due to the AC/20 + 3 SRM launcher meta rigs).
Many heavy-weapon mechs sacrifice speed. LRM dumbfire is great on them too.
LRM dumbfire works well against pop-and-squats; it keeps them pinned and busy instead of worrying about their flanks.
It really depends on how much ammo you have at your disposal. Missile boats have more to spend than front line mechs with LRM capability.
It may rarely be useful in a damage capacity, but it is very useful as a suppressive weapon.
Also without the lock, there is no warning. I've had 7 dumbfire kills in the past two years. [I don't do it often these days since I'm mostly using streaks and brawling mechs]. More than one of which complained about never getting an incoming missile warning. My most recent was in a Stalker champion if I'm not mistaken.
Edit: Doesn't look like I got the kill but I did get repeated dumbfire hits.
Vid time-skipped..
It's like sometimes firing a streak at an insanely long range is also super effective. Why? Easy: People cower behind rocks when they hear "Incoming missile." Scares the crap out of some players. Doesn't matter what it is or where it's coming from.
Edit: (Have-weapon = heavy weapon? I know I'm tired but damn.)
Edited by Koniving, 28 February 2014 - 12:19 PM.