+3 Voidbane Cannon
Just to simplify the math, let's say the stunning shot averages to half damage. HIstorical comp might be +2 Boom Stick, a popular enough token for the humor value. That token averages a bit under 8 damage. This averages over 12.5 damage and has +1 to hit. Enchanter's Whetstone really screwed UR weapon design, but that seems like a lot. Even if subtracted 4 from every result and decreased top end to 30 damage, would consider this vastly superior numerically to Boom Stick as null results on Boom Stick actually are far worse than losing damage wheel bonus. This never fails to deal missile damage bonus if it hits. Anything remotely resembling balance to that token would involve average damage being under Boom Stick's, likely by a lot, especially if going to get +1 to hit.
Now, I don't expect any effort to balance against old UR weapons. Numerous old UR weapons are trash. The +1 Voidbane Rifle averages a bit more than 6 damage a hit (meaningless drawback), up to 7+ with EW added in. Seems like a pretty big jump between 7ish and nearly 13, then an additional +1 to hit.
As a relic Voidbane Cannon would seem kind of powerful. Oh, we have a recent relic to comp against. +3 Fellbane Crossbow averages a bit more than 7 damage but also has an ability that theoretically makes it far deadlier than that. What do we approximate +15 damage against various monster types? One third of the time it will matter? Probably not half the time, certainly across multiple seasons. If say one third, then average damage is not far off, being over 12 in both cases but under 13. To hit is the same. So, this UR comps well to 2026 relic.
Now, how much does being Stunned matter? Well, if it happens on an attack round that doesn't kill monster, then not so good. OTOH, hitting for 40 + missile damage bonus makes good progress on there not being a round in which Stunned will matter.
Speaking of comps ...
Boots of the Plague
Someone might point out that Boots of the Four Winds only gives +6 damage (one assumes have Eldritch set if have this token), though it's a messy comp as this is more limited in a few ways.
More relevant comp seems to be Boots of the East Wind. Same rarity, for one thing. Now, Plague does more damage and affects multiple attack forms but has a drawback and poison is supposed to be a drawback even if it almost never matters. Might be able to argue that East Wind transmutes into something better, yet that something better doesn't do any more damage than Plague.
Kind of a shrug.
Now, 2026 has an UR feet damage increasing token. It has more versatility than Winds boots, making it a strict upgrade in isolation. It's +3 to damage. 2026, +3 damage feet. Then, 2027 +6 damage feet with one meaningful drawback. Seems like a significant gap.
Mask of Gaunt Luck
Seems like a pretty wide gap between +3 saves and trivial drawback to all of the masks below UR. Even +2 saves -5 HP seems a vast gap to lower rarity masks. The Epic may only be like relic power these days with power inflation unless consider face to be similar to back in how affect saves, but just this UR comes across already as relic power.