They do if you use the Multiple Attack Dice Optional Rule.
Yeah. When using Multiple Attacks, everyone gets to choose an extra target at a penalty and I believe Multi-Tasker can offset that. Might be time to start using that rule, especially since it also helps you get at least SOME damage through via multiple rolls instead of risking your entire damage amount on one die roll vs. high TMM.
If you're using Formations, things like Multi-Tasker and Demoralizer from Assault Lances can help, as can things like Speed Demon or Combat Intuition from other formations. There are also Special Command Abilities for your overall force that can help. Banking Initiative in particular is often helpful for planning counterattacks.
That said, AoE attacks, mines, and use of terrain can help a lot as others have said. Precision Ammo for autocannons can help too, if the unit in question has a decent AC special ability.
Using infantry to guard the flanks of your slower units can work, especially Power Armor. Infantry have a 360 arc of fire and do not take additional damage from being hit in the rear. Many can also inflict automatic Crit Rolls if they get close enough to a target, in ADDITION to whatever damage or HT they do at short range.
Multiple Attack Rolls, in particular, have gone a long way toward balancing swarms in our game. Most extreme swarm units are made of paper individually and one or two points of damage can cripple or kill.
Finally, I'd advise playing with Forced Withdrawal, which reduces the ability of swarm players to treat their units as expendable missiles instead of trained crews piloting valuable equipment.