Sorry for the inactivity. I've submitted my 2nd attempt. I replaced the Humans with Vieras this time. Almost every segment was improved, except for Totemas and final bosses, where I took longer due to lower levels.
http://tasvideos.org/forum/t/19420
https://www.youtube.com/watch?v=HvTbUXnGqpI
The combo idea could be interesting, seeing how I have two Warriors that can benefit from the Mythril Sword. JP at the end game, however, is far from 10, so I don't know how well that would go.
Edit: I recently considered using Aim: Vitals, which has a 5/101 chance of reducing enemy HP to 1. Unfortunately it doesn't work on bosses.
Edit 2: By my calculations, Combo would make the final bosses slightly faster, but:
a) at the cost of a much slower Materite Now (Totemas would use up JP, and the enemies start very far away from you), and much more menuing/re-equipping/AP watching
b) only the Estreledge Bangaa really benefits from the 5x multiplier - everyone else does <30 damage due to their low levels
c) it would be a one-time use, so only one of the final bosses (preferably Li-Grim, of course) would be faster
Granted, it could potentially take Li-Grim from a ~8HKO to an easy 2HKO. I'm just not sure if it's worth all that extra time.