I try not to weigh in too heavily on Rogue tokens, because I *know* I'm biased... but I'd like to try to address the Nightshade Gloves from the perspective of a (Grind) DM.
I learned, this past GHC, just how powerful the Assassin's Crossbow was in the hands of a Legendary Necklace Rogue. (At least, for an in-person event; being able to slide a 17 or better is much easier in real life, than it is in VTD.) In the hands of an experienced slider, combined with a supportive party ("Guys, I'm just outside the 17... someone bump me in?") the odds of getting that Critical is better than 50/50. Sure, it's only for 2 attacks per combat, but Rogues who have their build min/maxed for it can do some *serious* damage. It doesn't add up to the damage output of a Legendary min/maxed Monk, but it's still very impressive.
In order to get that amazing effect, however, Rogues need to equip:
* Legendary Necklace
* Assassin's Crossbow
* A UR token which lets them Sneak at Range
* UR Bead (or bracers) of Guided Strike (because the build is useless if you can't crit for some reason)
* various damage boosters to increase Ranged damage, which isn't *quite* as easy as equipping Str for Melee damage
So, yeah... that Triple Damage on a Crit is *awesome* but it's not really the Assassin's Crossbow alone which is "broken" ... it's the synergy between the Crossbow and Raphiel's. Even then, it takes some specific tokens to make it work.
The Nightshade gloves' original intent (if I understand correctly) was to give Melee Rogues a nice token which could deal out some Spicy damage in the hands of a skilled Rogue, as an answer to the Assassin's Crossbow. I still like that as a goal!
My preference (both as a DM, and as a Melee Rogue myself) is to have something which works:
* In Melee
* Provides or Synergizes with an expanded Critical range,
* and gives 3x damage *ON SNEAK ATTACKS ONLY*
By having it work in melee only, we're dodging any questions about how it stacks with the Assassin's Crossbow, as well as providing an alternate route to get that 3x crit
By giving it, or letting it synergize with, an expanded Critical range, we're making it a desirable token.
The very first iterations were 3x crit "only on a Nat 20" and honestly, I can't see anyone picking them up over a dozen other gloves in that case. A 20 in VTD is extremely unlikely (less than 1/20 chance) so you can go 2 or 3 VTD games easily without this kicking in. Even in live TD, it's really rare to get that 20.
Opening the crit range to 19-20 is where the token becomes viable to me. As a player, I'd love it to be even higher than that, but as a DM, I think that 19-20 range keeps the power in check.
I could also see letting it synergize with a wider crit range (with Raphiels) but if that's the case, I'd like to add the text of "once/combat" as that would keep it from getting truly out of hand.
As for that triple-crit being on Sneak Attacks Only... I think that plays well into the Rogue Class power. Rogues are about setting up for that massive damage hit, not about being triple-crit power-houses (that's Fighter territory).
In a world where the Assassin's Crossbow already exists, I think the following would be a balanced, but desirable token:
Nightshades Grim Gloves
3x damage on a Critical
melee-based Sneak Attack
once/combat
I think they'd also be balanced as:
3x damage on a 19-20
melee-based Sneak Attack
or, if you aren't all about the Sneak Attack, it could even be balanced as
3x damage on a Critical
melee attack
once/combat
My apologies for much wordiness.
I'd love to see this token make it through development.
I'd also like to see it not create a bigger problem than the Assassin's Crossbow ; )