Linzi, the adorable Halfling Bard was inspired in part by Lindsey Stirling, as well as the heroine of Kidnapping, Caucasian Style (1967).
A poll was held to see which new race would be added to the game. There were 3 contenders: the Aasimar, the Dhampir and the Elementals (which included the Sylphs, the Undines, the Ifrits and the Oreads). The Aasimar won by a very narrow margin and was added to the game. The Elementals came second while the Dhampir weren't even close to the top. Dhampir and Oreads would make it into Wrath of the Righteous, instead (with Oreads being a met stretch goal and Owlcat invoking a bit of "creator's prerogative" in making Dhampirs part of the base package).
Originally, there was a monk companion named Sakken planned, but he ended up being cut early on in development. This actually leaves a fairly prominent hole in the non-mercenary companion lineup, since without Sakken, Valerie is the only companion set up from the outset to be a tank.
Hellknight was a class considered to be added to the game, but budget constraint and time prevented its inclusion as a playable class. As many weary players will tell you, Hellknights are still... in the game, to be sure.
There's a Shout-Out to Warcraft II in the Back Room of the Kingdom's Tavern. If you click on one of the citizens enough times, he explodes, revealing a non-hostile fae dragon.