The term "splitter" can be ambiguous. I'm assuming the Dahua splitter you mentioned is actually a POE-powered 2-port ethernet switch. If you were connecting to that device from a POE switch on your network instead of an NVR port, I would expect it to work. From an NVR port I'm not able to answer. Another type of splitter is a device on both ends of the connection that would combine 2 of the NVR ports onto one cable at the NVR end, them break them back into 2 cables at the camera end. For this to work, the NVR ports would need to be using only 4 of the 8 wires in the network cable, which is probably the case but I don't have your type of NVR to confirm. An example of that type of combiner/splitter is here:
1-Pair RJ45 Ethernet Cable Combiner/Splitter, PoE 2-in-1 Cat5e/6 Data Adapter | eBay
I'm using this technique on a couple of cables with good results (with a standalone POE switch). If you build your own cables you can make it yourself. On the NVR end, it sends one port straight through on the orange and green pairs, and routes the other port's orange and green pairs onto the unused blue and brown pairs in the cable to the cameras, then reverses it on the camera end to orange and green pairs for both port connections. There are 2 other types of "splitters" that look physically the same, one to inject power on the blue and brown cable pairs, and the other that's just a simple parallel breakout of one RJ45 connector to two RJ45s, so you have to be careful to get the correct device, even though they can all be called a splitter.