I had a male guardian's voiceline in Moonrise towers and my guardian is female. Up until that point, everything was fine. Hearing a male guardian's voice threw me off guard for a minute. I thought to myself "Wait, isn't my guardian a human female?" and I had to think about it for a second. Unless in that case, they simply didn't record a female voice for that line?

Sometimes I hear hirelings say DUrge lines, despite not having the default DUrge voice sets. Maybe they are supposed to talk that way? I don't know.

I can't comment on Tav speaking DUrge lines, as all my characters have been DUrges so far.