Even though Volo is original and not a dandolion copy, I highly doubt he would have been in the game if it weren't for the Witcher 3.
Why not, he was in BG 1 & 2? I doubt the Witcher has much to do with this.
Volvo is suppose to be a wizard, though a pretty bad one, you may as well call him a "Rincewind wannabe", that about as accurate as calling him a "Dandelion wannabe"