Yeah basically instead of SAM tanking it at the beginning, or PLD, we are having the NIN doing so while everyone pops temps + finds magic procs.
bringing 6-8 blms intead of 4 make it so u can kill it with just ONE HQ proc, cause it's fana --> fool's --> proc --> fana --> dead.
If u bring more proccers, and you get HQ sword HQ katana, GL proccing before fana wears lol, that's a lot of WSs

Also SMN dmg is tied to Bloodpact recast, BLM can pull over 20k dmg in 3-4mins, assuming 2k thunderstorms SMN could pull max 6-8k in that timeframe.
Earthen armor isn't that useful b/c Scherzo alone is enough not to have BLMs oneshotted by thundaja/blizzaja, and WHM can cure BLMs so they don't have to waste time using potions and can keep on nuking.
Your strat is probably safer, and i'm sure it works well, however the longer the fight lasts the more dangerous it gets imho, and going with 6-8 BLMs is faster.
Almost all the blms we had were top-geared, capped skills and using macc equip + macc roll, still we were getting quite a bit of resists.
Will bringing only 4 blms + 2 cor be enough to kill it before it chainspells again?