As a Hunter, you're not exactly durable, but all you need to do is pick your fights carefully. My tips are:
1.) Stand back. Take enemies on one at a time. More or less applies to all classes, but moreso for the Hunter. Your scope jumps like crazy when you're shot or bludgeoned. If you're in room-to-room combat, use a revolver or a low-zoom sniper rifle.
2.) Try for criticals. Kinda obvious, but whatever. If you can't (no shame in doing it), go for the bodyshot. It's helpful to get used to criticals because later on you'll need to get good at plugging skulls (Crimson Lance). If you can, only use sniper rifles with 95+ accuracy. It'll help you nail those heads.
3.) Choose a build that you like. I personally switch between Sniper/Rogue and Gunslinger/Sniper. You can respec your skills anytime you like for a small fee.
irishstormtrooper said:
2. Stay away from repeaters. They're really just less accurate, less damaging, and lower rate of fire SMGs.
3. Don't use incendiary sniper rifles unless they're really good. Incendiary weapons, when they hit someone, set them on fire, concealing the shot area with flame. This isn't helpful for snipers, as if you get a headshot, their head is impossible to see until the fire wears off.
What Irish said. Keep off repeaters if you can. However, if you find a Double Thanatos [http://www.youtube.com/watch?v=eO2r5rf83QM] (which is like a bullet hose), hang on to it and see if you like it. I just got a Double Thanatos today and am ripping through everything right now.
As for incendiary sniper rifles, what you're looking for is called a Volcano. It'll be called " Volcano". It will be Legendary rank (Orange, Yellow, Dark Orange). The red text will say "Pele demands a sacrifice!", which means the bullet will deal massive AoE fire damage upon impact. If you get one of these, never let it go unless you find a better one.