I haven't played this yet but from what I've read, your groups will merge along the story. So, those items and xp that you gain aren't lost.
Also, the perma death thing is double-edge. Those that are so used to "easy" games will find it extremely annoying. I find perma death fun 'cause you just can't send your char in blindly.
Usually, these perma deaths are taken out when you play on easy mode. (At least the ones I've played)







