Curse of Strahd just got a whole lot easier. 

Facts

My god the balance team did not get the point with this one. Way to trivialize all vampire encounters by buffing such a low level spell. it was the ONE instance where a mislabeled spell was balanced.

Quote from GilneasHalfElven >>

Curse of Strahd just got a whole lot easier. 

 I'm planning to CoS with the new rules. This is a bummer indeed. 
However can't Strahd use fog cloud to dim the sunlight? In chapter two it says the following:

"By the will of the Dark Powers, the sun never fully shines in the lands of Barovia. Even during the day, the sky is dimmed by fog or storm clouds, or the light is strangely muted."

I hope your vampires have dispel magic or some kind of counterspell. Otherwise they’re screwed.

Still, this spell not counting as sunlight despite literally being called daylight was ridiculous. It’s a fine change to make.

Quote from Mdaddy >>

My god the balance team did not get the point with this one. Way to trivialize all vampire encounters by buffing such a low level spell. it was the ONE instance where a mislabeled spell was balanced.

 Or you could just upcast Darkness.

If you've ever played Five Nights at Freddy's- making the player economize the life of their flashlight adds a whole new level to the game

Quote from ZmF >>

Quote from GilneasHalfElven >>

Curse of Strahd just got a whole lot easier. 

 I'm planning to CoS with the new rules. This is a bummer indeed. 
However can't Strahd use fog cloud to dim the sunlight? In chapter two it says the following:

"By the will of the Dark Powers, the sun never fully shines in the lands of Barovia. Even during the day, the sky is dimmed by fog or storm clouds, or the light is strangely muted."

 
I think that only applies to the sun so unfortunately this spell is probably free game and I don't think fog will help, you need darkness and I'm not sure vampires have that spell. It's basically a COS win button at 5th level...

What the hell. This is SO stupid. 

*Salad Mixing Bowl

Fog is opaque if you're deep enough in it. Including deep enough into a fog cloud if you (the DM) want it to be... I would say that it doesn't completely negate the daylight spell, but it limits it to maybe a 5 or 10 foot radius for the full sunlight effect if it's in the fog, or only reaches about 5 to 10 feet into the fog if the daylight spell point of origin is outside the fog.

Or, since you're running Curse of Strahd and the land of Ravenloft is different, just house-rule it - but do notify your players in advance that that spell doesn't work as well in Strahd's area of control.

For this to be actual sun light, the radius needed to be much smaller.

20 foot radius equal to the darkness spell solves most of the issues

A 3rd level spell that does not require concentration producing "sunlight" in a 60 foot radius? Soooo stupid. Part of this game requires people GMing it, and this sort of crappy design makes that harder to run a balanced game.

Finaly the spell might actualy be usable, still a bit niche but it opens more options like when facing enemie with daylight sensitivity or vampires

This spell change to produce sunlight is a nuisance, rather than a threat, to any self-respecting vampire, let alone Count von Zarovich. Multiple responses suggest themselves: depart the sphere of effect, send a minion to remove the light source, throw a cloak over the brightness, and of course kill the caster (spite). Mage Hand, Counterspell, Dispel Magic, and an upcast Darkness are obvious magical counters. Good use of the spell should require creative use, for which it is fun to reward players.

I've run Curse of Strahd, and first worried about the Dawn spell, yet it proved to not be a decisive factor. I expect this to be the same for a prepared DM. And for a player, there are many attractive, competing options for the 3rd level spell slot. 

Makes Driftglobes a dangerous threat in CoS.  Three of them atop a Staff of Adornment, spinning around, 60 radiant damage a turn on Vampires... :D

Funfact.Astarion is in the illustration for this spell.

CoS already has a number of spells that simply don't function in Barovia. Just include this spell in there, or say the magic of the realm is too strong & suppresses the sunlight element.