Here's the first look at the new Rogue weapon.
Ok, ok, I know, I was thinking the same thing. "What the **** is this piece for?" But before you write it off completely, lets look at it a little bit closer.
Base damage - Good
This weapon is one die step up from normal, has 2.5 dice multiplier, and expanded threat. Imp Crit: Piercing really shines here. ~24/hit without imp crit, ~27 with
Damage/Attack mod - Good
Either STR or DEX. This is awesome if you are a dex rogue. There have been a lot more Dex rogues since the update due to Improved Sneak Attack requiring a base DEX score of 21. If this trend continues, I can see DEX/INT rogues becoming a lot more mainstream.
Rebellion - Good
25% reduced threat is never a bad thing for a rogue, but what makes this effect worth it is the 13-78 added piercing damage on a crit. Remember how this has an expanded crit range? Again, Imp Crit: Piercing really shines here. ~7/hit without imp crit, ~14 with
Sneak Attack Bonus +5 - Adds no inherent value
Because every decent rogue already has this on an item already. And chances are if you are running this raid, you are a decent rogue. You don't want to have to rely on equipping a specific weapon in order to get that bonus to hit and damage. SA on an item like Tharnes Goggles or the Tinker set is much more reliable.
Armor Piercing 15% - Ok
Situationally useful. It doesn't add a whole lot of value but it's a nice perk. Chances are if you equip this weapon, it's not for the armor piercing. I'm not UTD with the fort on mobs and bosses though.
Improved Deception - Good (maybe?)
As a rogue, soloing with deception is never a bad thing. It also stacks with deception equipped on an item. There once was a bug where the mob hit with the effect would aggro you (VERY problematic in raids where the tank is trying to hold aggro) but I'm not sure if that was corrected (hence the maybe).
So the item itself is pretty good overall. Here's the real question though. What weapon in your arsenal is it going to replace??? If you are soloing, you are running with Radiance weapons or Radiance + Epic Midnight Greetings in the off hand. The blindness effect is just too good to give up soloing. The real value in this weapon is when you are grouping and don't have to worry about aggro. This weapon deals more true damage than any other rogue weapon that I can think of (Edit: Agony is comparable, definitely wins if the target bleeds, Rebellion is definitely the highest damaging weapon with DEX as it's Attack/Damage mod though). Also, if you really get down to it, with the +5SA it also allows you to replace the Tharnes Goggles or Tinker set for something else like Dream visor while grouping.
FINAL VERDICT
This looks like a great group weapon that won't see much play just because it doesn't mesh well while soloing. If the +5SA was replaced with a +3 Assassinate DC, I could see this being much MUCH more popular. As far as grinding out gear though, I'm putting it on my "Nice to have, far from necessary" list.