Specifically, Make Love Not War and Us Or Them. These are the only non-power, constant, empire-wide global happiness boost laws. Make Love Not War is +20 per alliance and +10 per peace, Us Or Them is +20 per home system, Saints and Sinners is +20 empire wide and another +20 on a specific system from having a hero assigned as governor. All of these laws are politically thematic; Make Love Not War rewards users for having more alliances and peaces, Us Or Them rewards users for conquering other factions, and Saints and Sinners rewards users for having heroes assigned to systems. The problem is that Make Love Not War and Us Or Them can scale up far, far past the boost offered by Saints or Sinners. When in a 4-faction alliance, Make Love Not War is +60 empire-wide Happiness and can go even higher with peaceful status with outside-alliance factions. After taking two other home systems, Us Or Them is +60 empire-wide and can go much, much higher depending on how many other factions are in the game. Saints and Sinners only goes up to +40, ever, and will mostly be at +20 in systems with no hero assigned. This is particularly relevant to Vodyani, as I've found they can quite easily maintain a secondary Militarist or Pacifist party with election actions, so Saints and Sinners is directly competing with these laws for slots and influence. The problem is simply that Saints and Sinners doesn't scale empire-wide with anything, while the other two laws do.

So, since the Religious party is hero themed, why not have it scale empire-wide with the number of heroes in your empire or assigned to systems? Replacing its effect with something like +10 empire-wide Happiness per hero assigned as a governor would let it scale with something directly relevant to the Religious party's theme and bring it on-par with other happiness laws. Which of these three laws would be more powerful would depend on your empire's ratio of heros to alliances to home systems, rather than Saints and Sinners falling completely behind after a second alliance or conquered home system.

Let's harmstring that with "in governing parties" =D
I mean saints and sinners used to be braindead broken before.

Giving a +10 approval per hero on 20 heroes is more or less the same crazy stuff, but giving +5 on other hand is too trash to be reasonable to run.

So I guess limiting it by RNG you have little to no choice would be a popular go to fallback option as it is with federation "nerf" now.

It could be limited in multiple ways. Happiness per heroes as governor, happiness per heroes represented in senate, happiness based on total hero level, etc. I don't think more than one kind of conditional limitation would make sense from a user-readability perspective; it'd be simpler to just reduce the amount of happiness per met condition, rather than by adding a second condition. And you still have to get all those heroes in the first place.