I have to disagree with point 3 of this logic that leads to point 5, typically sweeping wind is up for a long time (obviously at least 20 seconds minimum), and blinding flash costs 10 spirit which will take less than a second to get.
Seeing as sweeping wind for non inna's will cost 70 spirit anyway, waiting an extra second for 80 spirit to cast blinding flash first will always be worthwhile for an additional 30% sweeping wind damage, so point 5 is entirely redundant, the logic should just go to 4 IMO.
Edit: I know this disregards the slight bonus of getting blinding flash up straight away, but I think it's always worthwhile when sweeping winds will typically be a decent DPS bonus for the next few minutes or more and realistically you will still get the same defensive bonus when it fires say 5 seconds or so later and you have the spirit.
well most of the people use the "tornado" build which has a last of 6seconds only...thats why !