The Batman Lego Movie is its own stand alone movie and isn't really connected to the original Lego Movie apart from Batman. It doesn't have any of the other characters, there's no mention of Wild Style for example.
My Lego Batman Review

So Voldy, Kong, etc. don't play a huge role? It's still a D.C./BATMAN movie at heart??

How long are those villains in the movie? Do they ruin or add to it?

You saw the movie already?
Yes the movie had advanced preview screenings.
Each individual villain does not get a huge amount of screen time with the exception of Joker, you do however get an awful lot of villains in the movie from Batman C list characters (movies words not mine) to a load of other villains from other films including
the likes of Jaws to Darleks
To make a great film you need three things - the script, the script and the script -Alfred Hitchcock

You saw the movie already?

Not a bunch of screen time, outside of Batman Robin Joker Barbra no one else gets more than bips of one liners here and there.

How much screen time do they get?

Bigger question is why Voldemort and Eye of LOTR and King Kong and Creature From The Black Lagoon are in this movie..if it's it's own universe.

To prove you wrong @ #3!
http://screenrant.com/lego-batman-movie-best-trivia-facts/?view=all

As much as I enjoyed Lego Movie and Unikitty this is not really set in the same universe, imagine a spoof movie of Batman done with Lego and that is what this film is more than a movie set in the world of Lego itself, some common themes do cross over though like master builder and such.
To make a great film you need three things - the script, the script and the script -Alfred Hitchcock

Alas, she didn't look both ways before crossing the street :C