Here are a number of thief bugs:
Deadly Aim (Trait): This trait causes tooltips of pistol traits to display the wrong values (as if the trait still gives -5% damage). It also has an 8 second cooldown displayed for no reason.
Preparedness/Sleight of Hand: The cooldown reduction granted by these traits stacks multiplicatively when applied to Deadeye's Mark/Steal, but additively when applied to Siphon.
Leeching Venoms: The lifesteal from this trait scales with allied Power and Healing Power rather than the Thief’s attributes. This trait also affects both the stolen skill Soul Stone Venom and Specter’s Rot Wallow Venom despite the trait stating that it only affects utility venoms. Leeching Venoms will only trigger on the final stack of Rot Wallow Venom.
Collateral Damage/Renewing Gaze/Payback: With auto-loot disabled, Deadeye’s Mark can be repeatedly cast on corpses to trigger all on-steal and on-death traits.
One in the Chamber: This trait does not provide a stolen skill if the cantrip's aftercast is interrupted for any reason (dodging, weapon swapping, etc...)
Panaku's Ambition: Cunning Salvo, Malicious Cunning Salvo, Hook Strike, and Death's Judgement do not trigger this trait.
Dark Sentry: When two Specters apply barrier to the same allied target, they reset each others cooldown of this trait (effectively allows both Specters to bypass the cooldown completely).
Traversing Dusk: The Shadow Force gained per friendly target has no cap on the maximum number of friendly targets.
Cunning Salvo/Malicious Cunning Salvo: The axe left on the ground by this skill falls through the ground in several raid encounters (preventing it from being recalled with a dual skill) including: VG, Sabetha, Mathias (only in part of arena), MO, SH, Largos, and Q1.
Malicious Cunning Salvo: This skill is missing its blast finisher (Cunning Salvo has a blast finisher).
Harrowing Storm: This skill does not count as a shadowstep for traits that trigger on shadowstep, but it does count as a shadowstep for triggering Relic of Peitha.
Death's Advance: This tooltip for this skill states “Number of Targets: 5” for no reason.
Ally-targeted Scepter Skills can grant their effects to 6 players if the targeted player is in a different subgroup.
Ally-targeted Scepter Skills that launch projectiles will only travel through 5 allied players before they disappear.
Shadowsquall/Malicious Shadowsquall: The ally targeted version of these skills apply Regeneration eight times, but any one target can only have five instances of Regeneration on them.
Malicious Shadowsquall: This skill has no healing power coefficient, has a lower base healing value than Shadowsquall, and its ally-targeted effects do not splash to nearby allies.
Endless Night: The ally targeted version of this skill applies Regeneration seven times, but any one target can only have five instances of Regeneration on them.
Venoms: When two or more Thieves use Venoms in the same group their overwrite and damage attribution are messed up. The Thief that casts second will overwrite all but the oldest stack; when a player attacks they will consume the newest (most recently applied) stack; the Thief that owns the oldest stack will be attributed the damage (the Thief that casts their Venom first steals all credit even though all but one of their stacks gets overwritten).
Ice Drake Venom: This skill applies twenty seconds of chill, but any one target can only have ten seconds of chill on them.
Impairing Daggers: This skill fires three projectiles but only has two projectile finishers
Mercy: Malicious Sneak Attack and Malicious Shadow Squall consume their Malice at the end of their animations; you can activate Mercy any time before either of these skills finish casting to get full value from Mercy as well as partial value from the respective Malicious Stealth Attack.
Shadow Force: When crossing a level scaling boundary in open world you lose all Shadow Force (i.e. if you travel from a lvl 45 area to a lvl 43 area you lose all Shadow Force).
Mind Shock: The circle indicator for this skill is affected by quickness, but the actual animation/hit of the skill is not. The tooltip for this skill references extending stability duration for each enemy struck but the skill does not have that functionality.