First of all, I like this change overall.
That said, there is a long history of the Gods cursing people with superpowers. An example would be vampirism: Cursed by God to be immortal, super-strong, nearly unkillable, and able to shapeshift. Some curse!
Some Greek legends attribute the transformation of Lamia from a normal human princess (hardly scary) into a massive terrifying beast that could only be killed by heroes of Hercules proportions to a curse from Hera.
This is, I think, the origin of the curse.
Also, it was always my understanding that Drider were savage and bestial, with the ferocious intelligence of the Drow turned into the simple bloodlustr and cunning of a beast. If we assume that the transformation of Drow into Drider comes with a loss of intelligence, ability, and perhaps even memory, then the nature of the curse becomes much more obvious.
That drider outcats would tend to form a sphere of dangerous creatures terrified of the drow but more than willing to kill intruders into drow areas also helps explain why Lloth would curse them in such a way.
So I think the previous version of the Drider makes sense. But the new version makes an equal amount of sense, and makes it much easier to incorporate Driders into Drow encounters.