That artstyle is so over-used and Original Sin should have an art-style which is more like Divine Divinity.
I tend to rather believe that the impression of "it is over-used" comes from persional bias.
Me, I have the other bias : To me, the "dark & grim" art style is over-used.
Skyrim, The Witcher series, Deus Ex, Demonicon, Blizzard, of course, Gothic series, Risen series, and especially shooters.
To me, therefore everything looks actually entirely different : If I look around me, I can see no light-themed (both in terms of graphics style ANd in terms in in-games themes) for the PC sinleplayer platdform anymore.
For consoles, it might be different. But we're talking about the PC platform here, I almost assume.
I begin to have the feeling as if this argument called "it is over-used" is being instrumentalized by BOTH sides now. Whichh each one wanting THEIR taste to be implemented.
Gothic : Arcania already had 2 different sets of graphics/textures. It would be a LOT of more work, but it would please more players. Imho.
I don't want grim and gritty, just something with a tone like original DD or DD2.
In the old forums, someone (not me !!!) wrote that - in this sense - ACTUAL REAL grass isn't as dark as presented within Divinity 1 ...
Just go out and compare the colours !