True, unless there is very specific use of "mister/miss" in jp raws like in Reign of Seven Spellblades. It's even in the anime and it sounds really out of place.Keep the honorifics as is. There's a few conventions that just don't translate into English.
-boyo
-dono
An older person calling a younger female -kun
An older person calling a younger male -chan
I got annoyed at one chapter by Platinum Scans where they had a highschool age character call a classmate "Mister" to denote respect and to show she wants to be his servant.