While I am not surprised that this last quest is not soloable, I am disheartened by the way that you are faced with this reality.
At the very least there should be a short mission where you go in and meet with the major story players, perhaps with a shot of Zhaitan in the distance, menacing and waiting. Guild Wars 2 Gold. With a clear sequence of dialogue that provides a measure of closure to the personal part of the storyline while making the case for the neccesity of a team to complete it.
Then at least the shock of marching all the way to the map point to find that you can’t do anything would be less disappointing. Cheap GW2 Gold.
Oh and not to mention, the risen abomination is invulnerable bug and the anchorage waypoint retaking is also bugged which are pretty important to getting to the last quest. The servers need to be restarted.