bizdev
I used Air Berlin about 30 times. Even on flights inside Germany I always heard German/English safety announcements. Whatever happened on your flight it seems to me being an exception. I agree with you that this could irritate someone not speaking German.
Flying pretty often these days (same carriers and same type of aircraft) I rarely pay attention to the safety briefing. BUT: whenever I fly on a different type/subtype I take my time to look where the emergency exists are located and I also have a look at the safety card.