The video shows that guards need heavy cover AND prone position to beat the Obers. And even then it's still a close fight. They would clearly lose in almost every other situation
If that's really a problem then get rid of the prone position ability. Or give it more drawbacks besides being stationary
Like others have said, I think the main issue with guards is the doctrines they are on. Guard motor is unquestionably OP and Mechanized support is still really strong even after getting nerfed
I think we are coming close but missing each other. In any situation the Guards lose so should the other Elites, however they have a situation as you described that has a 50% chance of winning. The generalist should not be able to outperform the dedicated squad especially in a easily replicable situation as both VG and cons can lay down coverage.
The doctrines themselves are a separate issue, they overperform due to how well the Abilities synergize with each other. Mark Target>Button>ISU152 is a nightmare to go against. But none of the abilities buff Guards in AI performance so not only do you have a unit that can pressure all infantry up to Obers you also have a Unit that can apply some sort of pressure to every enemy vehicle.
To show what I mean, lets replace long range squad for Long range Squad. If you place Airborne Guards for Regular Guards in Airborne Tactic it literally becomes even more powerful than Guards Motor. AT Strafe is back on the menu due to AT Strafe, while mid game is buffed even further due to additional INF presence instead of having to get a AT gun.
OR we can look at Terror Tactics which is already another great commander but more for team games. Button plus heavy bomb drop is now available against tanks. Little to no AI is lost due to Guards performance.
But if we look at it from the opposite and place Airborne into ANY of the Guards commanders it is an immediate downgrade.(Would probably actually help with balance)