Orks just got a cloaking device in their wargear, so they just got a huge leg up above Space Marines. Shush.
That thing is useless versus people who have a working pair of eyes. What the LSMs need is a reason to play Devastator.
More faction symmetry is better. Orks and CSM suck at sniping, SM get crushed at closer ranges, Eldar is very hard to do but can result in way better units if handled well. It is assymetric and thus not balanced at all.
What LSM players really need? That's all. A large percentage of the LSM faction being godawful is not a reason to buff the faction, the faction works perfectly fine and is more than competitive in some circumstances when played by organized groups. t. BLOP, VI, VM, XIII and many others.
This is because most of your playerbase is either new players or screeching morons that haven't figured out the objective or the dangerous end of their weapon. Coordinated LSM guildstomps are some of the most brutal guildstomps out there.
It doesn't even have to be a full guild. A single guildsquad mixed with semicompetent pubbies can completely dominate a game.