Hunters will have a very hard time against Death Knights. I think Death Knights will really separate the hunters who are good at PVP and those that are not good.
I have both a hunter and dk. Twice I have faced off against a hunter on my dk. The first time, he got me by surprise and i was not really paying attention and he got me. He was being a smart hunter and I was being a dumb dk. he was laying down frost trap and had serpent sting on me the whole time. that was him being smart. me being dumb was not using icy touch with death grip, not using strangulate, not using mind freeze, not using the stun ability of my ghoul.
The strengths of a dk are as follows:
-is that it is a plate wearer.
-it can heal if it hits you ( i have seen heals go off for 2k. this is done via death strike.)
-can have an obscene amount of health and armor (i am lvl 74 right now, and have 12,219 health with 47% dam reduction, if i go frost presence, it goes up to 13,495 health with 58% dam reduction. this is only quest reward greens and blues.)
-they can go unholy presence, that increases their speed by 15%, thereby making it easier to close the gap between them and you.
-they can have a pet, all the specs can get one.
-if they go unholy, they can get bone shield, that reduces all damage by 40% for 4 hits. (so, you can image how little damage you will be doing with auto attack if he goes frost presence and has bone shield up.)
-anti magic zone, nice little bubble of NO magic (arcane shot anyone?)
-my favorite 'oh crap' when tanking: ice bound fortitude. The Death Knight freezes her blood to become immune to Stun effects and reduce all damage taken by 50% for 12 seconds. Does not remove existing Stun effects.
when you look at what they have, they are going to be a very challenging opponent. do NOT, I repeat, do NOT take death knights lightly. they have a lot going for them. since they look for the same gear that warriors look for, you can expect to see death knights with health in the ranges of 15,000 - 20,000 easily.
the best thing for a hunter to do is to use frost traps slow them down, keep that serpent sting up. it will slowly take away life. remember, they can stop any magic in its tracks with anti magic shell, strangulate, and mind freeze, so auto shoot will be your only option. as a plate wearer, that damage will get reduced. keep your distance. i would really have to say, beast master hunters would have the best shot against them.
(by the way, the second encounter i had with a hunter was when i was a bit more aware. I was at a quest giver mounted when they both attacked. I was 72, they were 71 and had a 70 warrior. I ended up killing the warrior in ghoul form. When I made it back to my body, I popped a health pot, killed the hunter in a matter of seconds. Managed to bandage, the warrior rezzed back, killed him. summoned my ghoul and ate to full health, warrior rezzed, another alliance and him attacked me. I sent them both to the grave yard. i was in single digits for health.)