Nuendo’s MultiPanner is fine: in Ambisonic mode, it works as it should. But Nuendo’s Ambisonic decoders are a bit underwhelming, that’s why I’m suggesting 3rd-party software. As I said, if the target is fixed binaural, don’t bother going through an Ambisonic encoding: you’re not gaining anything.
The limits of binaural stereo are something that transcend a specific binaural panner or another: reading Jens Blauert’s Spatial Hearing can certainly put that in perpective.
Successful binaural panning depends a lot on the choice of sounds, the location acoustics, and expectations about the sound scene. Atmos for headphones or DTS:X are not more miraculous than, say, Sennheiser AMBEO Orbit. Some sounds, in real life or binaurally panned, will always remain difficult to localize.