Calculating Skill Delays

So pretty much every attack skill has a delay in the data, but how exactly is the delay affected by skills like Booster/SI/Yellow Aura/etc? I'd like to calculate the absolute fastest attacking speed possible with every speed buff active but I have no idea what to do with the initial skill delay to get there.

Mostly interested in Phantom Blow for now, which is currently 810ms, but after RED is 720ms.