Would expanding the Beguiling Influence invocation in this way cause any problems?

Question

One of the warlock's Eldritch Invocations, Beguilling Influence, bugs me. The full description is:

Beguiling Influence
You gain proficiency in the Deception and Persuasion skills.

This is fine for a warlock who doesn't already have proficiency with those two skills, but it's a bit weak for someone who already has one of them, and entirely useless for someone who already has both of them.

I was wondering whether it might help to get some more mileage out of this invocation if I were to change it to this:

Beguiling Influence
You gain proficiency in the Deception and Persuasion skills. If you are already proficient in either of those skills, you instead gain expertise with that skill, which means your proficiency bonus is doubled for any ability check you make with it, unless it is already benefiting from a feature, such as Expertise, that doubles your proficiency bonus.

The intention is that it wouldn't be any different for a warlock who wasn't already proficient, but for a character who was already quite deceptive and/or persuasive, this invocation would enhance their abilities even further. This, to my mind, fits with what I believe is the implied flavour of this invocation; that you are being supernaturally enhanced by your patron to be more deceptive/persuasive.

I added the clause about it not stacking with Expertise (wording borrowed from the Prodigy feat) so that it couldn't be exploited by a warlock/bard or some other combination.

My question is, does this seem like a good, clean change that would add to the game, or are there issues that would make this problematic, either 1) in terms of balance or 2) going against the design of what invocations are for, or 3) that would make it far less impactful than I'm expecting?

Answer 1

I can't see this imbalancing your game, but be cautious of favoritism/unfairness and stepping on the toes of Bard/Rogue

There are a great many features that grant proficiencies with no exceptions made for people who are already proficient in those things; as such, I would be cautious of making a change to this one Warlock feature and not the various other features as well.

Something else to keep in mind is that Expertise is mostly unique to Rogues and Bards so giving it to other classes might be stepping on their toes even more.

Also note that the Unearthed Arcana version of the Squat Nimbleness feat granted doubled proficiency if you were already proficient, but in its final release in Xanathar's Guide to Everything this was removed and replaced with advantage on checks to escape grapples. That doesn't necessarily mean the doubled proficiency was bad but for some reason they did remove it.

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Proficiency-granting features do a lot of different things

This is more just on overview of the various options available and their rarities.

Most features just grant proficiencies with no exceptions

I went through a list and the majority of proficiency-granting features do not have exceptions for those already proficient. This includes most of the feats that grant any sort of proficiency as well. Below are the few exceptions I was able to find:

A few features besides Expertise double your proficiency bonus:

The Scout Rogue's Survivalist feature grants them two skills proficiencies and a doubled proficiency bonus with those skills.

The Knowledge Cleric's Blessings of Knowledge feature grants them two skill proficiencies and a doubled proficiency bonus with those skills.

The Purple Dragon Knight Fighter's Royal Envoy feature grants them proficiency in Persuasion. If they are already proficient in Persuasion they can pick a different skill. Regardless, they get a doubled proficiency bonus with Persuasion.

The Prodigy feat is the only feat that lets you get doubled proficiency bonus on a skill.

A few features actually grant different proficiencies if you already proficient

The Artificer subclasses grant a tool proficiency, but if are already proficient in that tool you can pick a different one.

The Samurai Fighter's Elegant Courtier feature grants proficiency in Wisdom saving throws, but you can pick a different one if you already have that.

The Gloom Stalker Ranger's Iron Mind feature grants them proficiency in Wisdom saving throws, but you can pick a different one if you already have that.

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Somewhat related, a few features that grant darkvision extend your darkvision if you already have it. Most features that grant darkvision do no such thing.

Similarly, a select few features that grant spells give you different ones if you already know them. Most features that grant spells do no such thing.

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What I do at my own tables

When people end up acquiring a feature that grants them a proficiency they already have, I allow them to pick a different but thematically similar proficiency instead. This has not caused problems at my own tables, and means people don't have to worry about exactly what features are granting them what proficiencies. The main reason I do this is because I believe getting a useless feature is unfun and arguably bad design. The reason I do not give them doubled proficiency (expertise) is because I believe these should be left to the Rogue and Bard classes; skills are a lot of their entire thing/kit.

Answer 2

I doubt this solves the raised issue

I suppose your goal was to increase the number of equal choices warlock players would have, but keep in mind that the reason for a player's choice preference might be the importance of other invocations, not the supposed "weakness" of Beguilling Influence.

Let's see how players could build their characters using the standard rules:

1. Take deception/persuasion skills because they are important for the character concept, choose other invocations (not Beguilling Influence) because they are important for their build
2. Take other important skills, but since deception/persuasion are also important, take them via the invocation
3. Deception/persuasion are not important — take other important skills, take other important invocations
4. Take deception/persuasion skills because they are important for the character build, take Beguilling Influence invocation since other invocation are not so important for this particular build

Yes, choice #4 is meaningless, but 1-3 are equal valuable choices, and the "meaninglessness" of Beguilling Influence for #4 is not actually a problem since nothing forces the player to choose it. If I already have deception/persuasion skills, I choose another invocation, that's all.

Now let's say my DM buffed the Beguilling Influence (it is a buff, considering 5e bounded accuracy and the rarity of Expertise), this might disrupt the build I had in mind while was reading the PHB. Now options 1 and 2 becomes less valuable significantly. For real, if I could have an Expertise in skills I've already chose (so presumably they are important for my build), why don't take it?

As a result, instead of increasing the number of equal choices, my DM actually decreased it — now option 4 overweight other choices, especially options 1-2 (and nothing changes for option 3, when deception/persuasion are not important for my particular build).

Answer 3

From the Player's Handbook, regarding duplicate proficiencies (pg.124 PHB):

If a character would gain the same proficiency from two different sources, he or she can choose a different proficiency of the same kind (skill or tool) instead.

It's not explicitly called out in the wording of Beguiling Influence (most features that gain a proficiency use the language "If you already have this proficiency...", e.g. Artificer Battle Smith's Tool Proficiency), but it's also not called out that it does not allow substitution (the ones that do use the language "You gain proficiency in X if you don't already have it", e.g. Rogue Scout's Survivalist feature). In the absence of either, the PHB rule should take effect.

Personally I feel Warlock Invocations are very lightly-worded compared to other class features; for example, most of the features that grant the ability to cast without using a spell slot don't mention what level the spell is cast at (relevant for dispel magic), so it's not really surprising it's not made explicit.

So it's not weak if the player already has one or both of those proficiencies, since they can be replaced with any skill proficiency the player wants instead.

I'd lean away from granting Expertise, though. As mentioned above it treads on the Rogue's/Bard's territory; usually having ridiculously high skill check bonuses is the domain of the Rogue. Warlocks already have enough going for them, letting them get Expertise seems overpowered to me.