Changing Darkvision

[Garfunion]

Darkvision: You have superior vision in dark and dim conditions. You can see in dim light (removed distance) as if it were bright light, and darkness within "XXft" as if it were dim light. You can’t discern color in darkness, only shades of gray.
XX: based on race.

In what scenario with this change, would break the game?

[Specter]

It would make Perception/Investigation easier from afar, and also make some races mildly more potent than others. That''s it, I guess.

[rollingForInit]

It would make it a bit more annoying to play one of the few races that don't get darkvision.

If everyone is playing races that has it, I don't think it'll make any difference.

[Garfunion]

It would make Perception/Investigation easier from afar, and also make some races mildly more potent than others. That''s it, I guess.

The creature will still have to deal with trees, bushes, tallgrass, a wall and other stuff that will obscure their vision.

It would make it a bit more annoying to play one of the few races that don't get darkvision.

If everyone is playing races that has it, I don't think it'll make any difference.

Non-darkvision creatures in a group with darkvision creatures will still need to carry a torch to see. My new darkvision doesn't change this.

[Spiritchaser]

I think it will devalue being a rogue. It’ll impact other classes who focus on stealth, but rogues have a number of features which can or must key off of being hidden. This change will make situations where you can hide fewer and further between.

I wouldn’t do it for that reason alone. I think rogues are mostly fine where they are. Certainly I don’t think they need a reduction in power.

[Garfunion]

I think it will devalue being a rogue. It’ll impact other classes who focus on stealth, but rogues have a number of features which can or must key off of being hidden. This change will make situations where you can hide fewer and further between.

I wouldn’t do it for that reason alone. I think rogues are mostly fine where they are. Certainly I don’t think they need a reduction in power.

My change does not affect a rogue's ability to hide. To take the hide action you must start in a position that block creatures from seeing you(heavily obscured) like behind a wall, large tree, dense fog, total darkness,... Dim light only provides lightly obscured condition.

[Spiritchaser]

My change does not affect a rogue's ability to hide. To take the hide action you must start in a position that block creatures from seeing you(heavily obscured) like behind a wall, large tree, dense fog, total darkness,... Dim light only provides lightly obscured condition.

Well... no. The text in the older versions of the PHB states that the creature attempting to hide must not be seen, but that error was corrected in the formal errata, and the post errata printings contain the errata text:

They cannot be seen clearly.

This definition is a little vague, but it is reasonably certain that if you transition from dim light to normal lighting, you will make a lot of unclearly seen thieves and assasins all too clearly seen for their liking.

[Garfunion]

How often are you going to encounter at situation were dim light exceeds 60/120 feet. Excluding the daylight spell.

The reason for the change is I'm trying to remove additional bookkeeping/tracking of abilities. Streamlining it more for me as a DM. Rogues will have to simply adapt when dealing darkvision.

Edit: actually you convinced me. Instead of treating dim light as bright light I will simply remove the perception skill disadvantage in dimly lit conditions.

[Specter]

The creature will still have to deal with trees, bushes, tallgrass, a wall and other stuff that will obscure their vision.

These should be niche situations, not the norm. In a dungeon or a town, usually there won't be many things blocking the player's view in terms of corridors, streets and rooms. In these cases, you will need to be prepared to have players spot more enemies and traps.