Hmm, it wouldn't be too unreasonable to make a gear set which could hit that. Ariyala doesn't have Apple Streudel as an option yet, but that would push this set up to that Spell Speed threshold.
http://ffxiv.ariyala.com/TJKG

I tried swapping to my crafted hat for BLM, putting me at 889 Spell Speed, 2.29 tooltip GCD. Hitting the Deathflare right as the 1 disappears from the icon, seems safe enough. Not enough time to squeeze in a second Fester, but I think like it better that way.