When I worked out the individual spell damage and damage/MP ratios, I ended up with:
Basing this off of 380INT, 578MATK, 25 Fire Potency:
Thunder - ~400 damage, 1.9048 damage/MP
Thundara - ~800 damage, 2.1164 damage/MP
Fire - ~620 damage, 2.1088 damage/MP
Fira - ~900 damage, 1.7857 damage/MP
Firaga - ~1,250 damage, 1.7507 damage/MP
The ideal action "spam order" I wrote out (which I don't think any of us actually followed) was:
Parsimony, Excruciate, Quelling Strike (unless Collusion target), Resonance PREBUFF
Firaga first strike
Chameleon
Thunder
Thundara
Fire
Fira
Firaga
Fire
Thunder
Thundara
Fire
Fira
Convert
Firaga
Fire
Thunder
Thundara
Fire
Fira
Excruciate
Parsimony
Firaga <-- hopefully dead here
Thunder
Thundara
Fire
Fira
Thunder
Thundara
MP gone
Can also pop mega-potion of INT somewhere along the way. I pop mine before we start to maximize the first strike damage since I'm the collusion target; however, you'd probably max your damage output by using it some other time since you waste 10 seconds on the initial cast.
EDIT:
Thinking about things more, I find it interesting you guys have issues with Hearty Victuals (which are nasty) popping on the giltrap pop 60 seconds in since we get normal pops I think. This would imply your initial kill speed exceeds but then tapers off relative to ours.