UPDATE 1: Thanks to Light Buster for commenting saying the old way of earning XP has been patched.
UPDATE 2: Thanks to Nightwing DEU for mentioning you can't out level the targets, they are always above you.
There are a total of 24 Hunting quests in this game.
You can collect these quests by going to the Squadron PvP Area. You have to come back after finishing each quests or when unlocking a new area. Something to note is the Recommended Levels are not the levels of the targets, they are a lot higher then what the recommended level is. The last target might say recommend level 99 but they are a level 140.
As part of the new update, you no longer get XP for downing a enemy player that has been revived. A good way to farm would be to choose a dungeon that can be cleared and keep running that same one over and over for XP and bounty until a new way to farm XP is found.
Remnant Wasteland (Your find these to the left of the Floating Tower location)
Recommended Level: 13 Bounty Hunting 101
Recommended Level: 15 Lone Wolf and Gun
Recommended Level: 17 A Tempestuous Fighter
Recommended Level: 20 Ulterior Motives
Solitary Sands (if you look at the map, just to the right of the ship Graveyard your see a path leading to a shipping container area, thats where your find these marks)
Recommended Level: 21 A Numbers Game
Recommended Level: 24 Identity Crisis
Recommended Level: 27 A Dance in Twilight
Recommended Level: 29 VR Art Imitating Life
The Old South (These are all located at the back behind the Dome)
Recommended Level: 32 Might of the Cosmos
Recommended Level: 34 One in the Chamber
Recommended Level: 36 Every Dog Has His Day
Recommended Level: 36 A Nightime Stroll
Recommended Level: 37 A Demon's Gaze
Recommended Level: 40 Candy Party
Recommended Level: 44 Bathed in Moonlight
The Forgotten Woods (At the Forgotten Temple head to the right and go down the hill, your come across some players, kill these. Your then see a tower look up the hill a little and your see a small wall this is where the targets will be located.
Recommended Level: 47 Light and Shadow
Recommended Level: 50 Riding Numeric Waves
Solitary Sand (These next targets are located inside the Industrial Zone, so you not only have the people to contend with but the robots as well)
NOTE: The first two targets will say the Forgotten Temple, but there are located here.
Recommended Level: 52 VR Escapism
Recommended Level: 55 Solemn Atonement
Recommended Level: 58 The Meaning of Justice
Recommended Level: 75 A World Laid to Waste
Recommended Level: 80 You Are Already Dead
Recommended Level: 90 The Weight of Living
Recommended Level: 99 Glory Beyond the Veil