Now this posts is just going to be a summary of the changes I think they shoud apply to thif traits/skills to allow more diversity in builds (and make non-zerker thief not the only option in PvE).
First of all thief needs a condi weapon. Right now we only have dagger, pistol and shortbow which are all hybrid weapons. One of these needs more condi focus. Shortbow and pistol right now are absolutely terrible as ranged weapons and need a rework anyhow.
If they made dagger into the condi melee option, they should probably add condis to the auto-attack. A major buff to the ‘Dagger Training’ trait is also needed. To prevent spamming Death Blossom they could give it a Flip-over skill (the way it works with Sword/dagger)
If they decided on Shortbow as the condi ranged option they should also add condis to the auto-attack (and they could drop the bleed on pistol auto, making pistol a lot better too). Choking gass also needs to be improved (longer duration and maybe make the last pulse deal more poison).
As for traits: Right now thief also doesn’t really have a condi trait line. Deadly arts has condi traits but it also has ‘Improvisation’ (should be in Trickery imo), ‘Excecutioner’ and ‘Revealed training’ (should be in Shadow arts) making it more used for regular dmg builds. First of all ‘Dagger Mastery’ needs to be improved. If they changed traps to actually be usefull they could change ‘Deadly Trapper’ to inflict additional poison instead of vuln.
Shadow arts should probably also have some condi support as it also has the venoms trait. They could probably merge ’Shadow’s Embrace’ and ’Shadow’s rejuvenation’ to make room for a new adept trait. I would love to see a trait that adds poison dmg to stealth attacks, but it should probably be a Grandmaster. Maybe change ‘Rending Shade’ to something like that?
Next they should fix the currently worthless traps. First of all: make them circular! After they changed ranger traps (and removed the thrown traps ) to make ranger traps and DH traps more similar, one would expect to see a similar change to thief traps. Unfortunately Anet seems to have forgotten Thief actually has traps and has totally ignored them for the past 4 years.
If they change the trap trait to inflict additional poison on trigger traps could actually be usefull for condi builds. Needle Trap needs more dmg, and maybe they could remove the immobilize from it. Tripwire should probably be changed to ‘Snare Trap’ or something inflicting knockdown, cripple and torment (+poison from trait). Ambush can actually stay the way it is as long as they give the summoned thief a huge buff. Maybe give the thief a shortbow and let him inflict bleed on auto + use Choking gass/ cluster bomb? The thieves created with the ‘Thieves Guild’ elite could also use a buff.
If they decided to add the missing trap heal and elite that would be a bonus
Concerning Elite Skills: Dagger Storm would be more usefull if it had shorter cd and shorter duration.
If they would implement all these changes (which are honestly not that hard) I think Condi Thief could become a viable option.