Fair enough, the prospect of Spear and Arrow does buff that up a bit.
But you're wrong on the Balance potencies. read again.
"When it comes to Divination/Expanded-Balance, it's a similar situation, but it is a nerf.
Again factoring in redraws, you had a 26% chance to draw an Expanded-Balance over a minute*, you now have a virtually 100% chance to gain a full Divination over 3 minutes, so 33% efficiency in comparison to that 26%.
33% over 26% is... 126% as efficient, and at 6% instead of 5% damage up, it's another 16% more potent for a total of 142% of the averaged potency. Plug in the halved duration, and it's 71% as efficient as the old Expanded-Balance. If you want to give Divination a like-for-like potency, then it could be reduced to a 130s cooldown, therefore a neater 120s cooldown would actually be a slight buff."
You have a 26% chance of a 5% Expanded Balance each minute, for 30s. (which means this averaged out to once every 4 minutes)
You have a 100% chance of a 6% Divination every 3 minutes for 15s.
That makes Divination 71% as potent as Expanded-Balance.
There is no way that's 4,800 compared to 780.
Even adding in Spear and Arrow would only boost that by a maximum of a factor of 3 if you paradoxically simultaneously had all BRD/MNKs and all BLM/SAMs, so probably more like 2.5, and less considering Arrow doesn't match up to Spear, which itself doesn't match up to Balance, bringing it closer to a factor of 2, if that. So Divination would be, at a guess, maybe 35% as potent. (which I personally think is still overvaluing Spear/Arrow)
4,800 to 780 is only 16%.
This doesn't even factor in the fact that while you were fishing for an Expanded Balance, you weren't dishing out single target balances at the same time, it was one or the other.