Well if I'm soloing or lowman / tanking (which amazing enough happens constantly now that I have CDC) then Spontaneity is useful for an emergency Stoneskin or Utsusemi. This one time at band camp *cough* I mean while I was soloing WoTG missions. You had the demon + his four BLM's part, I spawned him as a RDM/NIN and proceded to fight the main guy and basically ignore his helpers. Went very well until they all went cheap mode, one did a -ga and the rest cast ST nukes all at the same time. Had me from full HP / Skin / Utsusemi down to 400 HP. Spontaneity Skin -> Utsusemi -> Cure IV x 2 then a CDC to finish off the NM. Glad I did it too cause right after I put it up they all swung at me.

Anyhow, lately I've found that I tend to tank accidentally on VWNM's. We all pop temps and I go CDC > Dusty Wing -> CDC -> Built TP -> CDC, usually get at least two if not three WS's off during the HV proc time. Then it's pretty much on me for awhile, I'm spamming Stoneskin / Blinks / Cure IV to stay alive, works pretty well as the PLD's will eventually pull hate off me, or the monster will kill me with a cheap shot ID move.