Steel Cyclone is great if you are in a situation where you cannot come out of Defience and are trying to maximize DPS with two or more enemies. If you don't need the mitigation from IB and there are two or more enemies it will always be a DPS gain to use it over IB. A perfect example of this is 4 Jagd Doll phase of A2S. Can't drop Defiance there but you can hit all 4 dolls with a 200 pot move that ignores your tank stance penalty. Steel Cyclone is also amazing for large trash pulls while running with a baller SMN. I will typically overpower, Eye combo an enemy for maim, Defensive CD, Bloodbath, Berserk, then Steel Cyclone, Infuriate, Deliverence, Decimate. With that I do metric fucktons of AoE DPS, self healing, and emnity while covering myself with CDs and allowing my SMN and BLM to go HAM on the trash.