You are absolutely right. The phasing issue occured because in VE Pro I accidentaly set the balance slider for the second group of Vl 1 to right channel only. Here is the file again, this time without that phasing:
https://app.box.com/s/wx4j85bycl4vtwclmj8n
Interesting that you find it doesn't sound like the Dimension Strings. It's really just that, without any effect whatsoever. It's only DS panned with PowerPan, and that's it. Maybe you find the way I set them up unfamiliar? Starting from Saxer's setup I made a preset with 10 Vl 1, 8 Vl 2, 6 violas, 6 celli, and 5 basses. Each section divided into two groups. For this snippet I recorded every group individually, which means two passes per section.