The Thief signets I hate significantly less than signets for other professions, but that's because you can trait to gain initiative when you use them. Then you can also trait to gain Might from using them. So while you lose the passive effect, you gain a lot of usefulness from using them... but not so useful that you want to spam them on CD - timing their usage properly is important even without considering the passive effect. You don't want to gain initiative when you're either full, or not in place to use it - and you don't want to gain Might unless you're about to hit them really hard.
The passive effect being there just means that holding them cooldowns doesn't punish you that bad.
My own signet-heavy build focused heavily on using CnD, but like Glytch said, it could translate well for your Pistol-focused build. The only problem with it is that you suddenly have a conflict of interests in the Critical Strikes line, because the following traits are all useful:
Signet Use
Fast Signets
Signets of Power
Ankle Shots
Pistol Mastery
And then, personally, I would also find a few of the other traits there useful just in general:
Combo Crit Chance
Critical Haste
Executioner
So imo, you could make such a build that would work, but... the truth is, in my personal opinion, you're over-loading yourself in regards to trait lines. It just seems wise to spread out a little bit so you can get full benefits.
Worth noting: You shouldn't worry
too much about the attributes you get from trait lines. They're useful, obviously, but from what I could tell, you get more from your gear. I especially noticed that a lot of the armor runes that were heavy on precision were also heavy on expertise or malice, so apparently conditions and crits go hand-in-hand.
Venoms isn't a bad way to go for Pistols in general. Your auto-attack stacks up Bleed, so it's not like it's
bad to go into Deadly Arts and Trickery. I still stand by the
two builds I linked you originally (weapons aren't quite right in those, due to mis-reading), one for offense and one for defense, if you want to stick it out with Venoms.
If you want to try a Venom-less build, for Pistols... I'd personally try this:
http://www.gw2builds.org/create/bwe_....2.1.10.2.9.12
Extreme mobility, plus caltrops for extra snaring (use right before the P/D-3), and since you might have to dodge a lot to stay away from melee... well, you gain Swiftness and Might from dodging! To help that, using Withdraw also gives you Vigor (I figure, you'd save Withdraw for when you can't dodge anymore, and you've taken some damage, or else just because you're snared).
Best part is having three ways to remove conditions, so you don't really need to get the Hard to Catch trait. (but if you REALLY want it, you can trade out Combined Tactics for it, though it makes the build have less initiative regen)
Possible tweak: move Combined Training into Trickery to grab the Uncatchable trait - this means that not only do you gain Might and Swiftness when you dodge, and gain some of that endurance back, but you also leave behind caltrops every time you dodge. (plus the added bonus of using Steal as a way to gain some init back)
You don't have much in the way of
damage conditions with this, but you can still stack up Vulnerability with your Pistol-2, and Stealing will still Poison and Weaken them, and like Glytch said you have your Cripples (both Dagger-4 and Pistol crits), so it's not that bad to have Expertise.
Hell, I think I should actually save these three builds in case I ever want to try 'em...