With my current Rogue Assassin setup (level 17), my opening move in combat (from range) has landed nearly 15,000 damage in a single attack before. Obviously that's enough to one-shot a lot enemies ... without me even being touched.
My two crafted daggers are 500 DPS and 431 DPS both with flanking damage bonuses.
Opening combat scenario is this:
1) Hit target with Assassin ability Mark of Doom as soon as they're in range. Mark of Doom upgrade also includes a 20% armor reduction on the target. This attack can connect from a pretty good distance, meaning I always get the first shot in. Mark of Doom stores 100% of all damage to a target for 8 seconds and then allows a detonation of the Mark to unleash all the stored damage.
2) After Mark, drop into Stealth which lasts 30 seconds and allows me to flank my target without even being seen. My Rogue also has several crit bonuses and damage bonuses for attacking from Stealth.
3) When I have the enemy flanked and while still in Stealth, attack with Overkill ... the upgrade to Hidden Blades which gives me 6 hits at 300% weapon damage.
4) Once the 6 hits from Overkill are done ... detonate Mark of Doom ... hitting the target again with the same damage amount from the initial 6 hits. The largest damage number I've seen from the Mark of Doom detonation was over 7,000. Total damage inflicted from Hidden Blades and Mark of Doom totaled over 14,000.