The math I did vs my guildies full glass cannon warrior put him about 5 to 10% behind me with a lot more survivability.
From the numbers I get out of annoying quite a few warriors asking their detailed damage, glass cannon warriors do about 4-5K direct dps, with a bit of bleed damage on top of that. So that 10% figure seems right. But after asking through lots of them, in dungeon typically they'd only do melee damage (optimal damage) less than 50% of the time, this figure goes up depends on how survivable the warrior is but for a glass cannon it means getting out of melee at the first sign of trouble. Staying in range would half his dps if not more.
This problem however is not as severe for thieves, since thieves can be reserving initiatives and dumping all the damage at once on an enemy when the chance is right, even though at range your damage halves as well (P/P doing 2-3K dps). Hence for damage comparison in dungeons, thieves are in fact quite a bit ahead of warriors.
More health is the only edge that glass cannon warriors have over thieves, which isn't much considering the aggressive playstyle and how hard dungeon mob hits. If a player is skilled at dodging and evading attacks he'd be able to survive as glass cannon, warrior OR thief. However, for a warrior any time spent dodging the attack/getting out of range/putting up defenses is time not doing damage. For a thief, again, this simply means saving up initiatives to unload all the damage later on. So a glass cannon warrior doesn't have the edge that glass cannon thieves have.
So really, the only glass cannon builds that synergize their abilities very well in dungeons are thieves and mesmers, that's about it, every other profession has to sacrifice more than just survival by going into glass cannon (evasive builds = lost damage up-time, which more or less defeat the purpose of going glass cannon). Not to mention that some professions just cannot do that kind of number period.
With that in mind, I have another question: in your judgement, how often in dungeons can your thief pull off that 6-7K dps numbers? (50%? 75%? 90%?) Even though thieves would take less penalty by evading attacks due to the initiatives system, in reality it probably is still a drawback, hence I'm wondering what the realistic numbers are like. Thanks again!