My earlier post seems to have been eaten. Forgive me if this is a repeat.
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I have reservations on the Grigori world spell.
SE is competitive in vanilla. In FFH it's almost a no-brainer. Food is far more common and easier to obtain. Cottages do not mature to the same level. The various doubling wonders and the soon-to-be-added specialist-boosting wonders are just icing on the cake. Even if you don't like the micromanagement required by the SE (and I very much don't) it's so much more powerful in FFH that you can ignore it.
GP production is a major part of that. Resetting the counter is a huge deal. Even if you pop the world spell after just a 6 or 7 GPs, that reduces the cost of all subsequent GPs by 500-600 points. With reasonable timing, the spell is the equivalent of giving all the Grigori leaders Philosophical, only it's a bit better because you can time a big wave of GPs all at once. Once the counter resets, the Grigori player is likely to have lots of cities with several hundred GPP. As soon as the counter resets, GPs are going to start popping as the game cycles through cities until the new threshold nears the prior levels.
Which brings up the question of how overflow is handled on GPs. If it is not loast - whoa momma! Not only will you have a wave of GPs over 1-2 turns, but you'll keep cranking them out for the next several turns. On the other hand, if there is not overflow, the Grigori player will want to micromanage GPP production - keep going with all the cities that will pop before the spell is finished and shut down all the others so GPP aren't wasted, then go back adn reset once the spell goes off.
Even without a GP UU for the Grigori, this would be a wickedly nasty ability.
With the ability to drop the spell right after setting up a GP Adventurer farm that cranks out 50+ GPP and a 80+% chance of Adventurers, it gives the Grigori the ability to pop out a flood of mid game adventurers in the course of about 20-30 turns for a virtual hero-army.