takes some problem solving. Pick your routes carefully, get behind if possible, and use your dumb teamates to your advantage. Some times mindless rushing in the open players can be better than a VSAT. No matter what Im playing I always have a class with an M8 as my primary, and MSMC as my secondary. Perfect for that scenario. Get some emp's flying, and some well placed cooked grenades, or C4 if your really a cool guy, and after a few frustrating deaths, the problem has a solution. Not to mention the frequency that you find yourself against a team of six LMG's with target finders is low. Have six of them actually puts them at a huge disadvantage as far as speed, CQC, and over all versatility.
Not only have I beat it. I often make at least one of them cry. Particularly if you are playing Demo, you have to know that it's spawn trap city. If you aren't good at breaking spawn traps then you are going to suffer no matter what gun/attachment combo is being used. The mere fact that they were sitting in corners makes them very predictable and easy targets for someone that understands the maps approach angles. While your kd is good your lack of adaptability makes you and easy target. What these guys did was show you the flaws in your gameplay. It's nothing to feel bad about but it is something to learn from. Each style of play has it's strengths and weaknesses. The reason that 6 LMGs with TFs on Demo doesn't concern me is I know exactly were the flaws are in their setup and how to exploit them for using it. You need to explore other playstyles in order to not only improve upon your own preferred style of playing but also to intimately understand the other strategies that will be used against you. Do that and you're kd will likely go down in the short term but in the long term it will bounce back and you'll come to appreciate what I already know. One trick ponies aren't difficult at all to beat.
You do understand that if you use cold blooded you basically are turning their target finder into a holographic site right? So do you have a problem with people using the holographic site as well?
I have a class setup that I like to use against TF people. Cold Blooded, Scavenger, and smoke grenades. They can't do anything if you run that class setup.
Spawn, Throw smoke to block the long sight lines, then flank them. Easy Peasy.