Disruptive Frontline Gameplay

[Scintilla]

I suggested shot-calling, because you seem to have come up against them often enough to have learned their tactics

You mentioned an FL guide for new players. I'm curious, what would you include in this guide which would be so profound that it would make premades suddenly survivable?

As others have said, shot-calling will do nothing.

DRK vokes, RPR removes Guard, followed by 2 BH5 DRG LBs. Simultaneously.

You've marked the DRK to try to get as much warning as possible of their coming.
Guard is going to be totally useless: regardless of whether you use it before or after the voke, the reduced movement speed won't let you escape in time before the RPR removes it and you'll still be caught in the LBs.
Stun the DRK or try to stand to attack? A nice try, but since their first attack which alerted you to their being there in the first place, they now have a high BH and an almost reckless alliance behind them - an alliance that knows chances of a solid counter attack are slim so they're safe to push further and harder than they would normally have done. Killing them will take longer and be much harder now they have BH. You may stun the DRK initially (but if you've used a melee to do it, good luck getting out of no-mans-land alive), but it will be removed far quicker than your team will be able to kill them. Some of your team may have already learnt their mistake from earlier and will have already begun to run. A few new players may not even be aware of the incoming danger.
Just run the moment you see them coming? Ignoring the fact that this would leave you having to completely give up objectives without any kind of counter-attack to defend them, if you've used sprint and you're early enough, you may escape. But remember: the only reason you escaped is because the DRK landed in a substantially large victim group that they remained there to voke. If all of you run, they'll just keep running after you, to the point where you're now nowhere near the objective.

I'm sure you've had moments where you're out of the deathball, looking at your team getting slaughtered and thinking "Man, if only they got out before the burst"

As said above, if everyone runs leaving only 3 people at the forefront of the enemy team, the DRK is going to run straight past them to catch up with a larger body of the team. Unless you all keep running for your lives until you're now far, far away from the objective, which you have no given them with no counter. If anyone got away, it's purely because a substantial number of their alliance didn't.

I think the best solution would be if they implemented a hidden rating system for FL queues

Ultimately, it will lead to the same veteran players being endlessly matched against the same premade teams, to the point where they just stop playing. So no, to believe that such a system will work shows naivety at best