No need of Cubase, except if you want to add recorded voices.
If it is the case, you do all your music in Dorico, export it to Cubase to add the voices.
Voices? You don't think people record many other things they would like to have integrated with a score?
What about dedicated hardware for Cubase? Video for film scoring?
Dorico doesn't even record MIDI performances.
There's a lot missing without being able to run a host DAW.