1. Man-at-Arms/Scoundrel/Water/Fire/Air/Earth/Witchcraft- 1
2. Dual Wielding/Scoundrel- 3
3. Witchcraft- 2
4. Water- 4 (Post lv 15)
5. Air/Scoundrel- 4
6. Dual Wielding- 5
*7. Willpower/Body Building +1-3
1. Far Out Man
2. Backstabber
3. Bully
4. Opportunist
5. Parry Master
* Know-it-All and/or Bigger and Better
Int +2 (7/9/11)
Dex +2 (7/9/11)
Con +1 (6/7/8)
OVERALL: As I describe below, this build is one of the best in the game, but not top two material due to not being able to use Grenades. This build would be used when you pick up Jahan (Jahan would have to be a pure Shadowblade with dual daggers as his stats won't support a dagger + axe/sword/mace hybrid hybrid) or if you are using a four person creation mod. Moderate early to mid but will become uber strong mid to end.
How to play early to mid: For almost all intents and purposes the Shadowblade plays just like the Dual Wizards save that he uses pure daggers and thus uses only his Dex. Give your Shadowblade the same skills as you would a dual: pick up Burning Touch, Firefly, and Wildfire (fire) + Teleport, Thunder Jump, and Shocking Touch (air) + Midnight Oil, Boulder Bash, and Summon Spider (Earth) + Freezing Touch, Rain, and Regeneration (Water) + Vampiric Touch, Decaying Touch (awesome when used with Regeneration in water) and Oath Of Desecration (Witchcraft) + Helping Hand, Melee Power Stance, and Battering Ram (Man-at-Arms) + Winged Feet, Fast Track, and Walk-in-Shadows (Scoundrel). Craft yourself dagger with +1 speed (on each) and keep them on at all costs until you can craft +2 Spd and then +3 Spd on your daggers. For the first 25-50% of the game you will find that you won't be dealing very much melee damage vs enemies who all take reduced from daggers, this is fine, the power in the build comes from its extra hp (from the Con) as well as its massive AP boost you gain from daggers (from the +6 Spd) mid-end game.
How to play mid to end: You will be able to deal more damage melee at this point in time, but frankly you will be using less melee from levels 15 to END overall as ranged master spells become available. The strength in the daggers is not in the actual daggers and backstab but in the extra +6 Spd you gain from using them. This massive AP boost when tied with Adrenaline (should be taken as a replacement for Fast Track around lv 15) makes the Shadowblade just as potent magically as the Ranger with her +3 Spd bow and Glass Cannon without sacrificing HP! Pick up Hail Attack in water, Storm in air when you hit 15.
Pro's of Build vs Dual:
-Massive AP
-Much greater HP pool
-Great magic output (due to AP)
Con's of Build vs Dual:
-Massively less melee damage output early-mid with less melee output mid-end
-Uses Dex as Prime vs Str means crappier gear all around
-Due to gear the extra HP may seem negligible as you take more damage across the board
Overall Thoughts on Build: Jahan builds into this seamlessly (pure build), making it a great fit. However, due to the massive loss in melee output early-mid when it matters the most and the extra AP and greater magic output coming mid-end game when you need it the least (it is more "overkill" than anything at that point) the build overall is not as good as the Dual Wielding. As a dual you will be dealing massive damage early-mid while the Shadowblade will struggle (grenades help a lot). As a dual you will be dealing massive damage mid-end with both melee and magic while the Shadowblade will be dealing either great damage with melee or even better damage with magic. Dual is very strong the whole game while Shadowblade will find his/her place somewhere between lvs 7-15 and have a stronger finish end (as magic will end up becoming more important). Because of this I would still say Ranger is the most powerful build in game, followed by Dual Wielding Grenade Wizard. I would also say that Jahan as Shadowblade would also make for one perfectly rounded party with Madora as the Leadership Knight, as she is very strong early and fades out a bit while the Shadowblade is the opposite.