These are symptoms of pretty much any core component failure, including hard drive and RAM. The only thing you have listed that would link the symptoms more strongly to your video card than any other component would be the "blue screen" in DR, which may even be a software issue. Are you experiencing any other kinds of problems that lead you to believe the problem lies specifically in the video card or motherboard?
Also depends what game type you're talking about. I most do dungeons and have played every profession a reasonable amount of time there. So, in no particular order:
Warrior: "should" have better defense but it's the profession that drops the most often, when plays run full berserker yet refuse to dodge.
Engineer: While they're not generally wanted so much in dungeon runs, I've found they have some of the highest defense with lots of tools/kits/elixirs that help them stay alive.
Mesmer: Are probably the best with a lot of distraction tools, clones, reflects, blink, invisibility etc. Yes you'll be vulnerable to the biggest hits, but it's easy to stay alive. There's also not much in the way of condition removal.
Elementalist: I find you either do massive damage or have decent defense. People are correct in saying with water and earth you have plenty of options. But more so than any other class; the more you put into defense, the more damage you lose. And it's a quick decline. But with good skill, class understanding, and a good build you can be an excellent addition to the group.
Necro: There's not a whole lot of condition removal, reflects or stun breakers, but with a high health pool, blinds, fear, death shroud, it means you have good survival rates.
Ranger: It's very easy to stay alive on a Ranger, but rather limited in damage, support/buffs for the group and not really wanted in most dungeon groups. With signet of stone, protect me etc you have plenty of emergency buttons.
Thief: While Thieves do have a lot of evades/stealth etc, in dungeons it's not that prevalent or useful (besides skipping mobs with shadow refuge or the evade on sword). With the low health pool and medium armour, they collapse very quickly.
Overall, poor elementalists (or ones running full zerker), theives and zerker warriors are the 3 professions I see downed the most. Guardians, Engineers and Mesmers are the best at staying alive, in my experience.
As a point of reference; most of my experience is in dungeons, mostly with competent players, but also plenty of the average pugs so this list isn't meant to be the best a profession can do, rather than the average you're likely to come across.
I don't know who's balancing over at ANet, but they've got no idea how to balance a class. Maining a thief myself, I was hoping the BS build would get toned down and other builds buffed slightly. Instead ANet decided they want everyone to run D/D...
I've shelved my thief and honestly I've lost a lot of interest in PvP after this patch. Another patch like the last one and I'll probably just uninstall.
Did you have fun getting them? Isn't Agnoy like Spectral Agony in GW1?
Did I have fun spending hours in WvW to get my gear with tokens for WvW? Yes.
Am I going to enjoy being forced to keep up with a power curve by grinding a PvE dungeon with gated content to keep an even playing field in WvW when my time is already limited? No.
Do I care all to particularly about the dungeon token gear? No.
Do I care that they are slipping down the slope of a power creep which murdered every aspect of GW1 from its PvP to its PvE? Yes.
Do I care that they gated their content with a nonsensical mechanic that I will have to keep updating to do more content? Yes. (So much for skill > gear. So much for everything GW1 stood for...)
Next up, they add gear progression to PvP because "thats what everyone wants".
I'd have seriously taken a dungeon full of Kohler as trash, boss, and mega boss mobs rather than some gated garbage. What is the point of gating? To add an artificial delay on the progression of your content. This has been WoW dance for as long as I can remember, locking people out of raids for a whole week after a single run. Why? To pad out the progression. And in there case it made sense, you were paying them monthly. In this case it makes *-all sense.
And there isn't a single reason provided for why the gear couldn't be exotic stats + best in slot gem + infusion slot. None.