First off, vanilla Orion accuracy is "okay" but I I personally think that his range and accuracy are somewhat underwhelming. So I edited his range in the DAVE editor and created a mini mod, increasing Orion's range from vanilla (like 160ish?) to 450, equivalent to a dwarf cannon. And his accuracy at anything above 300 meters is abysmal on some maps. I have trouble shoot this with every single modifier (Calibration_Distance, Calibration_Area, Spread etc.) to no avail. But on some maps Orion's accuracy is perfect at any range (400+ too).
I ask that you run an Orion Mortal Empire with a mini mod increasing his range to 450, and attack the initial beastmen army next to Orion. Place Orion in a position so he can fire at max distance at the enemy lord. See how his aim is way off.
AMATICALLY off. If it works please let me know!