There are definitely situations where thieves want to use this. There are situations where your accuracy is a bit low, think 80% or less. This can happen if you're fighting high level mobs or using meat, especially if your WS gear is otherwise lacking in dex/acc and/or if you don't have full dagger merits. In situations like these, 10 acc is major, and it couples very well with the 6 attack and 2-3 fStr boost from 12Str.
Generally when I'm talking about these situations, I'm talking about using Dancing Edge or Evisceration. For Shark Bite or Mandalic Stab, you don't need as much accuracy (given you'll be using SA/TA, for which DH's DEX/AGI mods will also matter more). Even if you're using SA/TA for DE or EV, it'll only help for the first hit. But these WS's are frequently used without SA/TA.
if you take off your acc other places and stick on dex in place this can become your best friend for all ws on thf, depends how youre geared, and base dmg of your main dagger though. i've yet to notice the mad little bunny yet though :x
Even with merc strokes unless I was soloing it without using SA or TA I'd use mirke or if I ever get it skadi. And without merc strokes I would never ever use this on thf.
This Body Piece is no doubt the best Weaponskilling body for any melee job that can wear it.
THF's do get a choice between this or DH and some will choose it over Heca but my opinion is that there is alot of other slots that can be used to stack on SATA stats and also most ppl nower days will have 2 jobs that can wear heca such as me WAR + THF.
It does definitely look cool. But it's not a full time piece of equipment. just about every weapon skill is modified by STR, so it makes for an awesome WS macro piece. most weapon skills are modified about 30%-60% STR. Dagger skills not so much, so i don't know why a THF would wear this...