The trick is to have at least one person with authority and clout to unify the different visions that can form in creative industries. Individuals do indeed have their own personal visions, and an effective leader can have the "master" (not in the master and slave sense, but final) vision but can also hear the visions of others to see how their visions can improve the master vision. However, any project where there isn't a clear vision of what is expected of everyone is doomed to fail.
From the interviews that we have seen, Tabata has the master vision of FFXV, and he has done an exceptional job of explaining what that vision is to customers and to his team. Given this communication, explanation of intent, teams can act more independently and require minimal supervision. So, they can take the vision and run with it adding their own flavors to it (flavors that are congruent to the master vision). This is the mark of a well running project, effective communication and shared vision. So, I think it is fair to say that you agree with me on that part. Your assertion is that a voice acting is better done in-person because they can communicate and better unite their visions into the unified vision.
I agree mostly. As I stated, there were sessions that they did this in FFXV English dub. What percentage of the final product is the result of these sessions is still unclear. However, my point is that with an effective director (who should and must have the "master" vision for voice acting, and that master vision has to conform to Tabata's "master" vision of the overall project) can take individual voice sessions and direct the actors to perform in accordance with that vision. The conversation that is most important is the conversation between the director and the actor. The actor can improve the master vision with their input, but ultimately, the actor has to fulfill their roles in the overall vision. Individual vision has to give way to the united vision of the project.
To use your scenario again, have you have been at work, and you and your co-workers are given a project. Each one of you is equal "rank", and no one is clearly in charge of the project. You all sit and discuss what you, as a team, are going to do. Some people think you should do X; others think you should do Y. You discuss it out, and you think you reached consensus. However, in practice, you all realized that you were thinking completely different things, and the project is delayed again and again while you try to discuss and argue over the details with no clear winners because as is the case many times, no option is clearly better than another. All options have a cost and a benefit. The project lacks an identity, and no one knows what's really going on. I can tell you from personal experience that project is not fun to work on, and more often than not, it ends up in disaster.
If we take my scenario, sitting in the recording booth and each actor has a different idea of what the story means, what their character is feeling, what the tone of the scene should be, and they play their parts the way they think best (fully intending to make the project successful), do you think we might end up with a 'one-liner' effect? Maybe the character performances won't gel? I am not saying this happened. I am only offering an alternative view to the idea that recording together is the answer. It isn't a promise of success.
Yes, if a cast naturally has chemistry and works well together, the director may not need to work as hard. (S)he can just layout the overall vision while the actors take the vision and run with it. The director only has to sand a few rough edges and keep the project on task. But, ultimately, the responsibility of ensuring the actor gives the performance needed lies with the director. So, even if the actors record on scenes months apart, (since I was watching LotR recently, I will remind you of the scenes in Bilbo's house with Bilbo and Gandalf. They were performing those scenes months apart and had to imagine the other's performance. Yet, it turned out great), they can still give the performance needed if they have a good director.
Now, I know you are mostly talking about anime and dubs, but this is a point that is applicable to many forms of media and industries. The issues you attributed to individuals is actually a failure in leadership. Effective leadership is hard to find, but from my perspective, Tabata is doing it right, and I trust his voice director to be doing it right too based on the interviews.