Before 1.0 launched, Mike said in one of his streams (or an interview?) that he felt like lots of people would be picking CoF at launch and would be quick to change to MG. That CoF was over-hyped and MG was still the stronger choice.
I don’t think they said this. CoF’s only purpose is to give way more drops than usual. You already have the target farming in-game, CoF just makes it so that, when you do target farm, instead of getting 1 drop you get 2 drops. Or 6. So you have better chances of finding what you want. Like they said in the patch notes:
This feels way too high. I don’t know where you’re from, but there are laws that prevent this in most EU countries. The normal value is 8h max per day, with 1h in between for lunch.
Anyway, I’m pretty sure that they can monitor the chat without having to be in the game, so they can watch multiple channels at once.
As for your solution, it’s not a solution. Bans are constantly being handed out. They just come back. They even had to disable family sharing because of this.
The point of CoF was never to be on equal ground as trading. It never will be. MG will always be better if you want to equip your characters fast.
CoF was simply the answer for: “We’re going to introduce trade. What can we do so that people that don’t trade (because they don’t like it, or have social phobias, or have to play offline, or whatever reason) don’t feel like the game experience is crappy for them like in PoE?”.
CoF is just a way to improve your drops if you don’t want to trade. So that you have better drop rates than MG. But it will never equal MG. It’s just not possible. Like you mentioned, even if you increase the drops by 1000%, there are still more people sharing in MG.