Guild Wars 2

“Glass cannon thieves can survive upwards of a ZERG.”

If you mean standing in the combined AoE of a zerg, then: No, they can’t.
They can, of course, shadowstep away and go into stealth. But that’s just what thieves do. As of now, in wvw they simply are the “roaming” class. Are they good at it? I’d say yes, probably better than most other classes (still depends on individual player skill, though).
But what I don’t get is this: Why should all classes and all builds be viable for every role and situation?
If you’re a glasscannon staff ele and get caught alone out in the open, you’re pretty much dead, no matter how skilled you might be. But that’s because you’re just not built for that situation.
A thief can’t fight in the frontline of a massive zerg battle like tanky warriors or guardians can. In a siege, they can’t pick of distant targets like a berserker Ranger or spam grenades like an engineer.
So the only situation, where thieves can become a problem, is when you meet them alone out in the field, which can easily be avoided by running with a group (or a zerg) or trying to build a balanced character, that is suited for a 1v1. Because most thieves themselves are build that way. And like mentioned earlier, they have to sacrifice other benefits for that and are useless in other roles.

“Cool..play a non stealth class and lets see you predict the ambush.”

As a thief, i’ve fought lots of good players who do exactly that. Engineers block (3 sec toolkit shield + 2 sec regular shield + 3 sec elixir f = 8 seconds invulnerability), Eles use their stun aura, mesmers stand inside their chaos storm, warriors use hammer knockdown etc. Or simply doge. A thief has max 3-4 seconds of stealth, so he will attack within that time frame. Keep moving. Run in circles to make it difficult for the thief to land his backstab. Try not to be predictable in your movement. But don’t just stand around or move slowly backwards, like so many people still do. (And maybe some advice for rangers or other pet classes: Keep your pet close to you – hitting the pet instead of the player is a huge waste of a backstab and initative.)
There are counters to thieves.
And if caught outside of stealth, they are extremely squishy. So stealth and fast reflexes are their only protection – they are “high risk, high reward” which is what I really like about them, and i hope Anet keeps them that way.
They might be difficult to adapt to, if you are fighting against them, but other classes can be tough too. Like those dagger-eles or tanky beastmaster Rangers with permanent regeneration and protection. Or Mesmers. Or unkillable guardians.
And I hope no one running around solo in wvw as a glascannon complains about getting downed by a roaming thief. Because that’s just asking for it…

@LameTerror

Sorry…
I was that Asura Thief in your video. They were quite persistent and keen on winning that glorious 3v1…
But you really kicked my “kitten” in that first fight. Should have switched to sword/dagger, which is what i normally use against eles.