Is my alternative to UA Revived Rogue’s Bolts from the Grave suitably powered?

The October 2019 Unearthed Arcana introduced the Revived archetype for Rogues, which while not being the most mechanically powerful archetype, has some fun flavour that fits very well into the gothic homebrew campaign I’m playing.

Probably the most-used feature is Bolts from the Grave:

Bolts from the Grave

3rd-level Revived feature

You have learned to unleash bolts of necrotic energy from within your revived body. Immediately after you use your Cunning Action, you can make a ranged spell attack against a creature within 30 feet of you, provided you haven’t used your Sneak Attack this turn. You are proficient with it, and you add your Dexterity modifier to its attack and damage rolls. A creature hit by this attack takes necrotic damage equal to your Sneak Attack. This uses your Sneak Attack for the turn

Working on the assumption that RAW, this allows the Rogue to inflict sneak attack damage twice per round by using their Bonus Action on (any) Cunning Action turn to unleash a Bolt from the Grave, then using their Action to ready an attack that fulfils the necessary conditions to do Sneak attack damage during someone else’s turn. Whether or not this is overpowered is not the question (it probably is…).

Compared with the rest of the party I’m doing a lot of damage, but although this is useful it’s also kind of boring because it slightly reduces the Rogue’s trademark flexibility and takes away their trademark single devastating attack. Obviously I don’t have to use the feature, but then I’m at a disadvantage because I’m not utilising a central part of my archetype.

So, I came up with this alternative version of Bolts from the Grave, and I’m interested in a mechanical analysis of this and to know this:

Is this overpowered relative to Bolts from the Grave?

I’d also be interested to know any thoughts about whether this is overpowered relative to other Rogue archetypes or in general, although obviously that’s a much more complicated question to answer.

Marked for the Grave

3rd-level Revived feature

When you hit a creature with a sneak attack, spirits of your past lives reach from the afterlife to help drag that creature to the depths of hell. They disrupt that creature’s attacks and defenses, and infest its wounds with malevolent energy. You are granted a pool of grave dice equal to your current sneak attack bonus lasting until the beginning of your next turn. Until then, when the affected creature attacks, is attacked, or is hit by an attack, may spend one grave die to grant one of the following effects, as appropriate:

  • When the affected creature makes an attack, the target may roll 1d6 and subtract this from the affected creature’s attack roll as the spirits slow the creature.
  • When the affected creature is attacked, the attacker may roll 1d6 and subtract this from the affected creature’s AC for this attack only as the spirits dull the creature’s reactions.
  • When an attack hits the affected creature, the attacker may add 1d6 necrotic damage to the damage of the attack as the wound festers.

The use of dice must be declared before rolling the relevant attack or damage. Only one dice can be used per attack.

The total damage incurred by this feature will never be more than that of Bolts from the Grave, and will likely be less. The benefits of the feature are shared out among the party in the form of a damage boost or an attack/defense buff (although in the form of a defense/attack debuff on the creature). On average, the attack/defense debuffs will be less than the effects of disadvantage (-3.5 as opposed to -5), so not enormous. Am I missing anything?

My DM is generally favourable to the idea of switching the feature out somehow, but wants to be sure it’s not overpowered in a way we haven’t thought about yet.