title_body: Is is okay that most consonant assimilations result in a phone whose dedicated letter doesn't exist?
upvoted_answer: I would argue that the orthography of your conlang is not just OK but really excellent given your description of the phonology.
  Why is this the case? It keeps the number of letters needed to write the language in a very comfortable range. The additional sounds are given by digraphs, a method that is often preferable over adding more letters to the basic alphabet or adding diacritics to the base letters.
  I also imagine that the orthography keeps morphemes recognisable assuming that at least some morphemes are just CVC syllables and combining them results in assimilation.