Hi stason,
Remember that we are talking about a non-linear phenomenon so we cannot think linearly in this case. Anyway, your thought is in the right direction.
In the past, when I was studying at the Univerdity of Aberdeen, Scotland (almost 20 years ago), I did a quick investigation on the sympathetic interaction with more than a transformer in operation. I will try to find where are those results to post in this forum.
Back to your question, let's think together, as this situation is not trivial (due to the non-linearities involved) so I cannot answer it straight (sorry!).
Let's consider that the transformers in operation have the same saturation curve. So they will saturate similarly and generating sympathetic currents with iqual shapes and values which will be added at the point of commom coupling. Of course, they will present a saturation condition different from that if just one transformer was in operation. Even so, we cannot say that "the transformers got saturated only half as bad" as you said.
Also, we cannot consider these transformers as an equivalent transformer with half of the original transformer resistance as the superposition principle cannot be applied on non-linear systems (transformer saturation).
Based on the above, I have just a feeling (not a confirmation) that the sympathetic interaction will die way slower than if just one transformer was involved.
stason, if you are interested in going dip on this subject I would suggest to write a paper together. I could go back to the 90,s to find my results and share with you. What do you think?
Best regards,
Herivelto Bronzeado