The misrepresentation lies in the assumption that without a mediator, the great crowd are without the covering of christ's ransom. Jehovah's Witnesses do not teach that. You confuse their teachings on mediator and propitiator. Damn it. I'm not supporting their teaching. I'm saying that their teaching is misrepresented.
The quotations you give us do not prove that they teach that the "great crowd" is without ransom benefits. All they prove is that Witnesses believe that there is no salvation outside the New Covenant arrangement.
You've made this mistake of assuming that because the quotations use the terms that concern you that they say what you seem to think. In fact they say the opposite. The articles you cite teach what I said they teach. Christ is the mediator of the New Covenant between God and Spiritual Israel. In Biblical terms a "mediator" is a contract negotiator. The contract in this case is the New Covenant. A "propitiator" is a peace maker, a reconciler. In terms of raw lexicographical definition, they get that right.
They reason that Spiritual Israel is a limited number, 144,000. This is probably wrong, but that's how they reason. What ever the number of Spiritual Israel, only they are in a relationship with Christ as "mediator." You confuse mediator with the concept of Christ as High Priest. Even witnesses recognize that he is high priest for all. As high priest he is "propitiator." As John says, that's for "not just our sins, but for those of the whole world."
I'm not telling you to accept Witness teaching. Some of this is questionable. But it IS what they teach. They do NOT teach that the great crowd, the rest of humanity, or anyone approaching God is without ransom covering.