Hi Michael. I'm running into a similar problem where my index building is taking a prohibitively long time (~7 hours to index a node property on 200M nodes). I've tried using this blockBasedPopulation but building the index with this setting enabled causes an out of memory crash. The index builds for a while (around an hour) with low memory usage. Then memory usage spikes, and the DB gets OOM-killed.
Any ideas on how this could be resolved? I'm using 3.5.6