Range is the key to PVP when using your Hunter. If you let the rogue, or other melee class get near you for more than 5 seconds, you may as well just lay down. You are a RANGED fighter, so use range or die.

Buy some gear!

Items that I use for PVP: Bow of Searing Arrows + Sniper Scope. Best arrows for your level + quiver. The best armor and gear available to you. Discombobulator Ray (made by engineers, I carry at least 2 - 5 shot rays with me always). Highest Health Potions you can get. Agility Potions, and any other stat bonus potions if you can afford them. (if not you should hunt more)

Shots used:
Concussion Shot
WIng Clip
SERPENT Sting
Rapid Fire
Arcane Shot

When in PVP mode, keep Track Hidden up always. Rogues will get the jump on you and you are dead before you can swing twice.

Here is how I beat melee classes up to 3 levels above me without a hitch: First off, make sure you hotkey your shots for quick access. You lose much time by fumbling with the mouse clicking. Keep your fingers on key and ready. Rogues and other melees are quick to jump on you and slice you to bits, and you won't have a chance in hell with even the best melee weapon.

Be aware of your situation, always,keep a sharp eye out, and be ready for anything. When horde hunting, i find a nice little hiding spot with some cover, and I try to use the terrain obstacles to my advantage. Be sly, you are a hunter, so HUNT.

Hunters Mark - ALWAYS.
Ice Trap: Then pull them into the Ice Trap with a Serpent Sting from MAXIMUM DISTANCE. I park my pet right on it, and have it set to attack freely so I don't have to click on Pet Attack. I often get tricky and place terrain obstacles between me and my target: trees, rocks, etc. This makes a great spot to place your trap.

Once he's slowed from the Ice Trap, fire Rapid Fire to get things rolling, keep moving backwards and strafing AWAY from them, then fire Concussion Shot. Keep backing up the entire time, keeping as much distance as possible. When the Concussion Shot breaks, you will be face to face with him, but don't melee, use your Wing Clip and get distance again, firing another Serpent Sting. (your auto fire will always kick in for you when you fire a new special).

Your Concussion Shot will be recharged by this time, so use it, back up again, and fire Arcane Shot and keep plugging away with your auto fire. If you find yourself in a tight spot where he has closed in on you, use your Discombobulator Ray immediately. This will slow him, and decrease his damage to you, allowing you AGAIN to get range between you and him, and keep firing till he drops. Its so cool watching a fat hordie turn into a Leper Gnome!

Do use your arcane shot for finishing touches and for extra damage when you can. If you keep your cool, and don't panic, you can drop most any melee player with this method, even a couple levels above you. Don't be afraid to use a Health Potion or a Clicky Heal item when needed.

Feign Death is your last option. Most times if I screw up, I will take it like a man and just go down honorably (except for when fighting you smelly hordies!).