Similar issue for me since the last patch: About 1/4 of NPC dialog is missing, no mouth movement, all cut-scenes (multiple classes/characters/plot points/scout maps). My character always has audio when she/he speaks.
I don’t know if this is related, I didn’t notice until the audio cut out, but the audio when it does play lags behind the mouth movement for all NPCs — but this may be something that was present before and I didn’t notice. It’s not an obnoxious period of delay, but it seems noteworthy.