We are running with 2 zones, 2 loggregators in each zone. I thought the same thing. Stopping all but one loggregator showed the same results.

If it helps, yesterday I was seeing 75% of the logs make it through with 4 loggregators and about 90% when I bumped the node count to 8. So it isn't always a 50/50.

Also, after shutting down or restarting a node, I see almost 100% of the logs come through at first. Then it slowly degrades back to 50% after a few minutes.