(sorry for triple post, but 2nd one couldn't fit this info in it XD)
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As you can see, the only cd not 100% active for Barrage's first duration is IR, and it still has 75% uptime during it. After that BfB and HE both pair of up with Barrage's second cycle, while RS's 2nd and IR's 3rd pair up with QS's 2nd as well.

That was what I had the best parser results with. I tried 7 different combinations, including ones discussed ITT and this one came out in the lead. I can only assume because of the cd uptimes during both Barrages.