I haven't played PvP in a while, but here's what I remember while playing:
Defense received several HUGE buffs in the new PvP system. First, they introduced Elusivity, which reduces the value of your socketed accuracy. Second, they granted almost all ATs some amount of global +resistance to all while in PvP zones. With the diminishing returns hammering many sets like ELA that rely solely on high resistance, defense sets got a second form of free buff by having their reduced defense augmented by free global resistance to all. Sets like ELA push resistance so high on their own that outside buffs do very little-- including Power Surge.
Even more disconcerting for resistance sets is the new mez system, which nearly guarantees a hold can be placed on a resistance character for several seconds. Defense grants protection from holds by inducing misses, and defense sets receive the same value of mez resistance. This is another huge benefit for defense, and resistance sets again got the short end of the stick in this regard.
If you are serious about PvPing, I would do a few things.
To hit most toons, you will need to far exceed 95% accuracy in your attacks. I would recommend using purples and other sets to stack global accuracy and exceed 175% accuracy per attack, ideally landing above 200%. You will need to have your Build Up socketed for ToHit buff, obviously, and should also use a Kismet + accuracy.
As far as dieing so easily, you also must use IOs to overcome some of the inherent benefits that defense has and resistance lacks. I found that my toon in PvP spec was more effective by stacking mez resistance. Aegis (20%) and 5 sets of Impervious Skin globals (37.5%) will make a surprising difference when it comes to getting mezzed. Resistance sets should already have a slightly higher mez resistance in their toggles, but they don't. You have to use IOs to fill in this gap.
Oh yes-- take Taunt as well. The skill applies -75% range in PvP. It's an absolute priority if you want to do well. Do note that Taunt requires accuracy in PvP, and I'd recommend 6 slotting it for accuracy, recharge, and range.
The system changed again and Defense is now basically out the window. I suggest checking out the PvP forums to get a better understanding of the current mechanics.
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What build should I go for in PvP? Right now I noticed all my attacks miss, even with acc at 100+%, even when I use buildup I miss a lot, but I see people 3-4 shot me when I have power surge/thermal buffs on.
I'm lost. : /