I got 53 seconds (including sharing bonus) using Piz'fer^, Jennish^, Bahamut^ and Odin^; only good enough for rank 554 now (it was rank 83 last night). Comparable results are probably achievable without any SS^ units - just Baha^, Odin^, Levi^ (for their column and cross(all) attacks) and a strong melee fourth. All four SS^ mages are probably required to reduce the final boss pincer from a double pincer action to a single pincer action, which is what you're seeing in the top 50.