As stated in the "Lighting Tower," when the Emperor first came to Dorn's home planet, Dorn face a thousand warships with Phalanx.
Now this may be an example of arrogance or concession, but with Dorn's strategic background, one could infer that the Phalanx was capable of taking on all of the Imperial warships, and Dorn knowing this met them face to face.
Hope this helps.
" I dropped my modeling knife so I bent down to pick it up. At the same the phone started ringing, so I put the knife in my ear and the phone on the desk. The scar is still there..."