I'm glad Kevin Conroy and the original B:TAS Robin/Nightwing are back for this. But, I'm irritated that they went for another B-list TV actor instead of hiring a real voice actor. Last time I checked, Tara Strong is readily available, and she's the person who is basically the main voice of Harley Quinn now. This isn't a "New 52" based DC animated movie where most of the voice actors are B/C list tv actors, and if they're already bringing Conroy and original Nightwing back why not go with actual voice actors for the whole movie?
Contrary to popular belief, being a (good) voice actor is not easy, and just being a regular actor doesn't mean someone will do well as a voice actor (as Jason O'Mara proves by being a good live action actor in Agents of SHIELD but a terrible voice actor for Batman in the New 52 based DC movies). Some people can do both, like Mark Hamil, Nathon Fillion, most of the people Pixar/Disney casts in things, etc. But, usually normal actors hired for voice acting jobs because they have a bit of name recognition are mediocre at best, terrible at worst.
Still, I'm definitely interested in the movie. Hopefully Bruce Timm can make up for his involvement in the horrible Killing Joke movie. Plus, maybe Rauch will turn out to be one of the surprisingly successful actors trying voice acting (she does have a few voice roles on her filmography, but its all little kid stuff, and one role as a baby).