I'm currently finishing an arrangement in Sibelius. One of the last things I'm adding is dynamic markings. For context, there is a string section, an electric guitar, electric bass, piano and vocals in the score. I have a good understanding of dynamics in general, but a poor understanding when it comes to percussion. Does a drum kit follow the same rules as more orchestral instruments regarding dynamics? I feel like telling a drummer to play certain passages pianissimo, for example, would make no sense.
All percussion instruments can be played at varying dynamic levels, so that includes snare, toms, hi-hat, cymbals and kick. So, certainly, dynamics need writing in for any percussion parts when appropriate. Just bear in mind that something like guitar at 'mp' might need certain drums to be marked 'pp' to retain a sensible level between them. But realise all markings are relative.