Anyone that has already tried to do this will know that you can't convert a party to a raid if there is someone from another realm in your group.
I just figured out a way that you can get up to 4 Real ID friends into a raid with you:
- Invite someone from your realm to a group and convert to a raid
- Walk inside the raid and convert it back to a party
- Invite your Real ID friends to the group
- Use the mass summon guild perk to summon them inside
I was wondering whether or not this would be classed as an exploit? You can still only have 5 people in the instance, which is the same as any other cross-realm dungeon. It's useful for boosting a lower level friend through an old raid or 5manning a 10man raid.