ok guys, this is how ive seen it done, been told HOW its done, and done it myself :
1st off to be able to do a SATA + ws you need tp, so:
#1 : need a acc / atk / STR / haste set to build tp and do good dmg while doing so. typically SH, swift belt, and things like that is what you want to use in this set.
#2 : your SATA set. Needs a crap ton of +dex and +agi gear to be able to get a good boost in dmg. Emp. hairpin, Leaping boots, +dex rings, drone earrings are good for this set. Optionally you can have 2 sets, if you split up SATA, SA is based off dex and TA off agi. So, you can have an agi set for TA, and a dex set for SA if you split it up. But doing SATA together, you want to find a balance of the 2.
#3 : The only dagger's dmg that will affect your WS is your main hand. Your offhand can be a 1 dmg dagger, and the WS still do the same dmg if it was a 25 dmg dagger (given any +agi or +dex stats taken away would change the dmg). So you can use a high dmg dagger in your main hand, say a corsair's knife at lv 50 (dmg 21 and atk +10) to enhance your base dmg of the WS before SATAs dmg kicks in, and then use an off-hand that gives some good bonus stats while still doing decent dmg for TP building.
#4 : as far as ive seen INT doesnt do anything for steal, but it does help on picking locks... havent tested mugging yet. Alot of the THF AF is more situational gear that you macro in for steal, or use for farming... most of it i wouldn't use in exp parties unless you really couldn't afford anything better.
just make /equip macros to switch between your TP build set and your SATA set
but as many others said here, there are quite a few ways to play thf... find the best one for your play style