I think that Ghaul (post Homecoming) is several time stronger than oryx and other creature in the Universe.
Start with a comparation
Traveler power=Deep power.
The Traveler power is now concentrated in the hands of ghaul.
The Deep power is divided in 5 worms god: Akka Yul Eir Ur Xol. We know that oryx eated Akka and with a good probability not only he.
So if We put Ghaul at 10 Teo a scale of power, Oryx will be 2 or Max 6.
So Oryx, a extremly powerful creature will be a little sh1t compared to the Emperor