I joined a raid group to do the tuskarr family achievement. Went to the area (lunker sighting below ruby life pools), but everyone else was in a different phase. Tried going to Valdrakken as suggested by the outdated message on the raid frames stating to go to a sanctuary like Oribos to properly phase with my party, but it didn’t help.
Eventually four others joined the raid that were in my phase. Those stayed with me as everyone else left. I tried to find five more but everytime I added people to my group from group finder, some people who weren’t phased became phased. I then invited a druid of the same faction I saw running around next to me in the world because we needed one more player but inviting him to my group phased him out of our shard completely even though he was standing right next to me before joining.
My friends kept changing to alts so I could invite them and refresh the group and get everyone in the same phase, somehow this worked even though I remained the party leader. As everyone came into the same shard, the talking head from the world quest would activate like I just entered the area.
On top of the harpoon randomly selecting the wrong lunker or thresher for half the group, this was a very annoying achievement to obtain. I didn’t try any other locations since another group did this in a large raid without issue just before I got there.
As an aside, nobody was in war mode and the inconsistency of the phasing didn’t seem to indicate it was related to any campaign or quest progress since various groups who weren’t phased prior became phased and vice versa. Party sync was not available as an option.
Originally, all were horde, so it wasn’t a faction issue. I added one alliance later on and that did not cause a problem.
We did finally get the achievement after much finagling.