NWN2db is indeed close and still, after all these years, a great tool to get an idea about your build.
Sometime in the future we will perhaps not need it anymore, I remember the staff hinting about a "live module" where you can build and test your chars directly in the servers' environment. (crossing fingers for that to actually happen!)
About sneakers and feinters: there are indeed a couple things that aren't obvious from the beginning but at the same time mantadory.
(1) If you want to use stealth/feint reliably you need to focus on it.
You either get your hide/move silently (and bluff, respectively) to 65++ or you should not go for it at all since you'll be rather disappointed in the high level areas.
Even with numbers above 80 (which I never managed to reach here, by the way - but I keep reading of chars with hide/ms/bluff in the 90s even

) there will be areas where your ability (stealth/feint) is close to useless.
If you're interested in the actual formulas for determining success/fail of these systems, I'll happily send you a PM - I do not want to derail this thread into another discussion about htese, systems, though.
(2) Focusing your build on stealth/feint doesn't suffice - you need highend equipment, too.
Before the inclusion of the hell shop (whose items are nowaday distributed to various merchants, Kalehir at the Wide + the travelling merchant at Beregost among them) it was almost impossible to become a successful stealther or feinter without the help of established players and/or muling and/or a lot of luck.
With those items implemented you now have a terribly expensive but at least freely available source of equipment that can put you into the 60s or even 70s for those three skills, provided your build sports base skills of 45+ (hide/MS) and 40+ (bluff)
You will probably suffer in other areas (AC, AB, and saves come to mind, but also elemental resistances), though.
(3) Playing a stealther or feinter is kind of different from playing other classes like fighter. If you just recklessly charge into enemy groups you'll probably die a lot. tactics are key with this kind of chars.
Which brings me to your question about Epic Precision, PTWF and Epic Dodge.
Epic Precision is a must if you don't want to run from any skeleton you encounter. The Fields of the Dead are quite frightening to any DEX-based char, but without EP (or other means to deal damage to crit-immune monsters) you are not going to succeed there.
PTWF - the question just is: do I want to deal damage as quickly as possible as to avoid beign hit (low AC and saves, remember) or do I take the risk? I will, whenever possible, want the chance to deal damage from double the amount of attacks.
Epic Dodge - is basically a non-deniable +5 AC in 1vs 1 fights.
So yes, I want all three of them. And everything else, too.
