For PvP, try to craft/find gear with the Impenetrable trait. That should lessen the blow of critical hits. Also, are you magicka or stamina focused? If you're a stamina NB using a melee weapon or a bow, you might want to pick up some medium armor. If using DW, Steel Tornado is an AoE that could help you if you get stuck in a mob. 2h is indeed quite devastating, but that doesn't mean you have to use it to do damage. Pick up skills in your weapon/NB tree that stun/cause immobilization/slow movement speed and take advantage of that (as others seem to be doing to you). It's tough to go full melee (IMO, anyway) in Cyrodiil, as it's so much easier to snipe people from afar with a bow/staff. It's also tough to run solo when most people are grouped up and have numbers on you. If it's that first hit that's getting you every time, then learn to expect it and bait it out, making sure to either block or dodge, and then counter. Skirt around the enemy, do the unexpected, and learn what abilities at your disposal hit hardest.

Ok first thing is first are u non-vet or vet? If your vet do not wear heavy p9parmored. No need for it. The best thing about heavy armor is the increased armor. In non vet u do not get this bonus. All armor is the same unless u have a weapon trait or mundus stone. So go med/light cause the passives are crucial in nonvet. If you are indeed vet I would go 2 pc heavy and the rest either light or medium which leads me to next question...

Are you stamina or magicka? Stam build in pvp go medium and then light for magicka. It sounds like you are stamina build. I love my DW in pvp. One DW is the best way to go even if u want to use a magika build. As a side note if your talking vet pvp fo 2 pc heavy and 5 pc medium. In nonvet I go 5pc med 2 pc light for some more versatility. For stam build I like steel tornado for aoe which is the strongest aoe in game. Rapid strike is my other favorite. For class abilities power drawn gives a nice buff and supreme attack is a must for nb stam dps. Killers blade is great for a finisher. Ambush is your gap closer.

Also fear, relentless focus blur and shadow cloack are magicka dumps. He'll I have run two DW weapons at same time with hidden blade on one bar for range. 2 gear setups could be night silence 5pc or way of arena for nonvet or hundings rage perhaps for vet with ashen grip. For dps

Also do u want to run 2 DW bars or DW bow or what...

in nonvet dw/resto is viable give me a little bit and i will get a build up for you that should work well. however keep in mind there is no one build fits all. i will provide a guideline in which u can the tweak and alter to what you are trying to accomplish with your playstyle and what is most comfortable for you to use.

I mean I have been running a dw/bow nb since beta. I like it and will continue to do it while it is popular and long after it has passed. Play how u want.

i would go with 7 pc med. if you have someone who can craft 9 traits then i would go with the 5pc set that gives you 2 mundus stone traits. then i would get the mundus stone for weapon damage and stamina. this will give you a nice damage boost.
if no 9 trait crafters , then go with 8 trait way of the arena. this will allow you to break free w/o using up all your stamina and allowing you to continue to attack or dodge roll.

if neither of them are available to you then go with the 4 trait set white strakes for a solid damage sheild. this set works well with the vamp passive that reduces damage at low health by 50%.

a nice 2 trait craft set, if those ones are out of reach, the 2 trait set deathwind is a nice set to give you a second to breath and regen some resources.

the way i presented those are the order i would put them if available. (I usually recomend the night silence set but since your a vamp you get that passive already.)

as for a trait on the gear i would go with mundus stone trait. although i do like the suggestion mentioned in another comment, i think for dps this will be a nice extra boost especially if you use the 9 trait set that gives two mundus stones. that said, impen is a nice one to use for non-vet, but the problem i have is a lot of players dont have high crit. the lower players inherently do not have high crit. even somone with champ points will have low crit. a higher level player with crit but no champ points still wont have a great crit chance. a player with champ points and higher level probably wont stack crit but penetration. however, there is an argument for using it and i use it on my temp, so i will let you choose. (my temp is geared toward resource regen and sustainability, so a different situation.) either way if you get the 9 trait set i highly suggestthe mundus stone. others is could go either way.

main bar: DW (go with 2 maces with sharpened trait for armor pen.)
-dark cloak (works well with suprise attack, get away, and removing DoTs. also, a magicka dump)
-killer's blade/steel tornado (execute) (killer's blade for solo ganking, steel tornado for groups)
-ambush (gap closer and increases damage of next attack)
-suprise attack (main dps) (you can also put rapid strikes here. i like both and leave the decision to so. SUprise attack works well with Dark cloack. if you use rapid strike here then put dark cloak on your other bar. in which case i would put sap essence on this bar to really buff up your attack and heal you. and yes this is the magicka morph which will work well in non-vet)
-fear (this is your CC and it is your best friend)

-ultimate: death stroke (powerful ultimate that is real cheap and works well combined with ambush)

Back bar: Bow
-poison injection (this is your dot and gets stronger with low health targets)
-bombard (this is a nice aoe for the bow and goes through DK wings) (i would say if you used
-lethal arrow (this has a great for distance and heal debuff)
-dark cloak/sap essence (choose the opposite of what you chose on main bar)
-relentless focus/peircing mark (relentless focus is good for the stam recovery and the 8% damage bonus. peircing mark is good to counter stealthy NB. this is also a matter of preference.)

-ult: vamp ult (get the healing one combined with sap essence and you will come back from the dead when fighting a group. you can also choose the one that makes you invisible so people have trouble hitting you and works well with suprise attack)(this is also relatively cheap.)

another skill you can think about adding in the rotation would be the vamp skill that turns invisible and mitigates 75% of damage. this will help with surviving. or perhaps blur in the rotation will be nice. play around with it see what you think. also, if you find yourself running out of magika to quickly think about running 2pc light and 5pc med. should solve your problem.

make sure all your jewelry is enchanted with reduce stamina cost of abilities. only reduce cost of abilities work in non-vet.

again, play with the build and see what is comfortable for you. everyone is different. this is merely a guideline and what i would setup for non-vet not more vet pvp.

good luck!!!

i personally think 2H is clunky and slow animations. i have also ran around w/o a stam heal since beta and it works fine. with rally dropping in alliance rank/ the buff to hidden blade/ the speed of dw/ using to glyohs and having an extra weapon pc for a set. you cant go wrong. but yes i completely agree that the 2H heal is what is real nice. imo comes down to preference and play style.

Disclaimer: Didn't read all other posts because I found something to comment on in the first answer you got, so may be a repeat.

Impenetrable gear is very much useless nowadays. You have more damage mitigation by using reinforced on heavy armor pieces and nirnhoned on other armor type pieces, even after the upcoming nerf to nirnhoned. If it is crits you die to, either train blocking more or try to up your evasion game.

It also depends very much on your build. I assume you are stamina based - in that case you need to have more medium armor. The resource regeneration (windwalker passive) and defensive ability cost reduction (athlete passive) are very central to any stamina based build. Wear at least 5 pieces and complement it with two heavy armor pieces for survivability boost.

Also, blur is a good starting point. Make sure you use the double take morph for added mobility. Also, remember to shadow abilities. Every time you use a shadow ability, you increase armor/spell resist by 5000 for a couple seconds - build these abilities into your damage rotations for constant uptime.

Remember the fear. This does both, get the people off your backside and provides the shadow barrier passive mentioned above. In general, use as much CC as possible. Work of AoE attacks whenever you cannot focus a single target and go hit & run over follow through. If you don't drop your opponent immediately, get out. Double Take, animation cancel by dodge roll, get distance, cloak and ambush back in. Try to stun opponents - the incapacitating strike ultimate is quite nice for this in dense situations.

In general, never stay stationary. Mobility makes it more difficult for others to hit you and is the only real defense a nightblade has. It also opens more opportunity to employ cloak + attack combos that provide short time stuns. In view of the upcoming changes do not fall into the perma-dodge trap, but learn to weave dodge rolls into your attack combos. May sound stupid but this is what many high class stamina melee NBs do instinctively - just watch them on the field.

Lose the resto staff - as stamina build the heals/utility from it are less than negligible. If you need more utility, pick up S'n'B for defensive stance and invasion for a good spell defense and offensive CC boost. The obvious choice would be 2H, since it provides the two things mentioned above as well as a stamina heal, but I will not recommend that cause I hate it with a passion (**)

One universal hint would be to make sure you have 3/3 Medicinal Use (Alchemy passive) and a full stack of tri-pots and damage/stamina pots. Also, Vigor is stupid OP if you have access to it.

If you are going for the Magicka NB route, then you need to build up around Cloak usage. Train maneuvering the battle field with maximum stealth usage before focusing on your damage abilities. DW can actually be a decent weapon choice for that, especially in combination with resto. Your build would than have only class abilities, so again you need cloak and possibly fear on your offensive bar. Cloak - Ambush - Concealed - Soul Harvest - Cloak - Speed Pot would be a classical combination.

This build can be incredibly strong and bursty, once you unlock proximity detonation (6k Ambush plus 20k Prox is death for most) Again, nirnhoned or sharpened weapons are mandatory for this kind of build. Here you can go with a 5 light / 2 medium split (the medium for stamina boost) and your whole play needs to be based on enemies never seeing what hit them.

Also Mirror Image is probably more or less mandatory, if you intend to go against more than just a couple opponents and are not yet firm enough in the cloak game.

A melee magicka nightblade probably has the steepest learning curve, maneuvering the battlefield is again the key but much more limited (due to missing gap extenders like dodge roll and bow passive) and solely based around cloak.

I hope I could give some pointers as to what you need to improve for the change from range to melee. Let me just say that it is a completely different game.
(**) Sideline Rant: How can you make one weapon line that provides high damage in combination with CC - Wrecking Blow and Crit Rush, a gap closer - Crit Rush again, a heal/DPS boost - Momentum/Rally, a universal execute plus execute range damage boost - Executioner, and a spammable all-damage-shield - Brawler; while at the same time having the second highest damage of all weapons available? Make sure that designer is locked into a campaign solo with two resto staves and 10'000 2H opponents hunting him 24/7 for the next 10 years, please!

If survivability is your issue, you might want to look up what is usually refered to as "sap tank". Magicka based, but one of the most durable builds in the game atm ( and from what we can tell even more so after 1.7 ).