You should list a Substitute set with leftovers as a set.
252 SpA, 252 Spe, 4 SpD
Quiver Dance
Substitute
Fire Dance
Bug Buzz
This set loses out on a bit of coverage, but allows for setup on pokes that rely on status. For example, Substituting on the switch to Thundurus, or using Substitute to block a possible T-wave or Leech Seed from Ferrothorn. This also gives Volcarona a fighting chance against Chansey and Blissey, blocking their respective statuses and forcing Seismic Tosses. This takes some prediction work, but I find it to be worth it in the end.