It’s unorthodox, but the back court has been working when the two have shared the court together. In fact, the Holiday/Frazier pairing has a net rating of +19.7, including a defensive rating of 89.1–which would be tops in the league by far.
So why is this working so well?
There are a lot of factors, but the main is that the players, at least offensively, are fairly complimentary. With Holiday as the primary, pick and roll ball handler, Frazier is allowed to work off ball more and a shooter and slasher. Look at his shot chart below.