Not anything to brag about really, but… I suppose you can take it as an example that if someone as bad/poor as me can do it, then you can as well. :p
Thief in full Berserker gear (Exotic, two ascended pieces). I used Bowl of Orrian Truffle and Meat Stew (100% chance to gain 1 stack of Might when dodging, 40% faster endurance regeneration) as a consumable.
30 Acrobatics
Vigorous Recovery (III) – I wanted to be able to dodge often seeing as I felt like I was made of cake instead of flesh and bone if Liadri ever got a chance to smack me.
Fleet of Foot (VII) – Allows you to remove the dangerous conditions Liadri inflicts if you accidentally get hit without having to waste a skill slot (and far more often, to boot).
Assassins’ Reward (X) – Just to keep some healing and sustain going. Needless to say, I got hit rather often despite being able to dodge a lot.
20 Shadow Arts
Slowed Pulse (II) – I really only went this because I wasn’t using any Deception skills. Everything else feels rather useless considering that Stealth behaves rather kooky in the Queen’s Gauntlet in general.
Power Shots (VII) – I was primarily using my short bow, so the extra damage was appreciated.
20 Deadly Arts
Venomous Strength (IV) – For the damage, I was having issues with it.
Quick Venoms (VIII) – Again, higher poison up-time for the damage. I suppose I could’ve replaced either one with Potent Poison (V) as well.
Only used my Short Bow. All my other weapons were melee, which felt like a bad idea as a squishy Thief.
Skills
Withdraw – Low cooldown for high Vigour uptime and also grants an extra evade if things go hairy.
Spider Venom – Condition damage.
Skale Venom – More condition damage!
Scorpion Wire – For pulling clones so I could get to phase 2 quickly. I let the first and third walk normally into the zones of light, I pulled the second.
Thieves Guild – Some extra burst, though they’d usually die pretty quickly.
Rather simple strategy. Get through phase 1 as quickly as possible and then run around in circles while shooting down Liadri. Due to the jump/chain nature of the Short Bow’s auto-attack, my poison charges would usually end up being wasted on her clones, but I still managed to get her down shortly after I popped my venoms for the third time, so I suppose the battle took 2 minutes or so. The Short Bow’s second skill has the quirk of not being obstructed by the Orbs, meaning that you can safely take them out from range.
This strategy would’ve likely been less painful with a Carrion gear setup, some Tuning Crystals and if I could afford to go deeper into the Trickery tree, but the things you do when you can’t afford a new gearset at a whim. :p