The initial quest requires level 15, but to join in the instance/FATEs however it's a level 50 cap, and trust me a level 23 character would be one-shotted several times over in there! So I think it means you really need to be around 45-50 to enter at least (if you're over level 50 you'll be level synced down), not surprising given it's a replica of the end of 1.0 events and level 50 was the level cap available in 1.0.