How to get to Ashengate, Reliquary of Scale
First, in order to reach Ashengate, you'll need to travel to Direwind Cliffs. There's a few different ways to get to this zone, you can have a Wizard port you to Sunderock Springs and run north, you can have a Druid port you to Direwind Cliffs directly... Or the last option is to take the Guild Hall portal to Goru'kar Mesa and travel through Sunderock to reach Direwind Cliffs. If you'd like more information on that journey, follow the link provided.
Once you are in Direwind Cliffs comes the most difficult part of this journey, traveling north through the zone to Ashengate. There are some enemies along the way that will see through invis, sometimes there's a named up in the northeastern portion of the zone in the same area you run across all of the wooden bridges that will see through invis....
But most commonly, the place you'll encounter enemies that see through invis is just south of the huge camp of Drakkins in northern most Direwind Cliffs. Just outside the gate to this camp of Drakkin enemies you'll run into two large Guardians of the Gate NPCs. These guys see through invis and can pack a pretty mean punch.