Please tell me this isn't working as intended.. 1 shot for over 40k in less than a second..

[DeceiverX.8361]

Assassin's Signet D/P BD damage mod build.18k is actually pretty low to be honest.

The only real culprit here is extended OOC stealth on D/P + DrD. Otherwise, you could have easily lived because everything after the backstab was when you were downed, and can dodge/negate everything else while taking minimal damage. Vault is easy to interrupt/blind/dodge out of, and the thief burned his whole initiative bar for those three skills.

Damage being high isn't a problem. If you play a glass build which can blow people up, people can do the same. Mesmer is 100% able to deal comparable damage, with a build designed around pure burst easily able to shatter combo for well into the 30-40k mark into light armor base defenses while stunlocking their target. Ranger playing Sic 'Em Soulbeast with QZ+OWP can do the same thing in strictly less time from range with more mobility. Rifle Warrior is the same. Same with nuke DH/Guard, fire ele, power reaper/scourge, glass holo, etc. etc. If you can't react fast enough, you die. Welcome to playing a high-risk burst build.

Damage is fine. Play D/D power thief in berserker gear and tell me how good it is. It does more damage, but it's complete trash. Damage with no visual tells (ooc/ranged stealth) and high degrees of safety and with failsafes, like what D/P Daredevil (and soulbeast, and mirage, and holo) offers, is not.