Thanks again for all the work you are doing.
Keep in mind that although Garuda's Wind Slash is a 3s CD, for testing purposes it does seem to work as Shinryu says, that it's a little bit higher, whether that is due to the AI not pre-queing skills or w/e.
On the quick testing I did a few pages back (edited my post so it may not have been noticed) I decided on low Crit, with Garuda doing 5 minute trials. This seemed to alleviate most of the procs interfering with data. Unfortunately, those short tests show such a small difference it's hard to get any sort of comparison even with the +377 Spell Speed that I used.
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One idea may be that if Ifrit's AA is confirmed @ X time, then you could always directly compare any results to his # of AA's. (assuming his AA isn't somehow effected by SPD too, and assuming that neither AA or Skills are delayed by any level of clipping from each other)
If the parse runs long enough then it could possibly even out any effect that procing EP has on the data so that you could correct for it.