A number of things should be considered now that we have experience with large groups of players on two servers.
1. Spawn rate - it is rather high, perhaps too high.
2. Despawn time. A high level wraith can be a nightmare for lower levels questing or deeding in the area. It is now far too easy for someone to grief lower level players by spawning a wraith in their quest area and then just leaving.
3. Wraiths in non-group instances, including missions. Given that one goal of the wraiths is to encourage cooperation between players, and that is not a factor in these instances, perhaps they should not spawn there.
4. Difficulty of wraiths. At low level before characters get many of their important abilities, such as corruption removal, it can be almost impossible for some classes to solo even normal wraiths. Not everyone has a family of crafters to gear them up as soon as they hit level 7 or 10, nor should gameplay be designed to almost require that. This becomes far more of an issue when lower levels are not as jammed and this will occur quite soon. IMO tone them down at least before level 20 so any class can fight a wraith with a good chance of winning. The challenge will still be there since we will get wraiths at very bad times while fighting other mobs - and will get higher level wraiths from other players.
5. Wraith level. Is it reasonable to have elite master wraiths sometimes spawn on us? Are those now something that we are expected to be able to solo routinely? Or is the design intent to have our own routine wraiths (not the Nine) be a "feets don't fail me now" event?