I am DM in a campaign and recently my players reached level 3. The Rogue chose to take the Inquisitive archetype.
I am looking at the Eye for Detail feature, which allows the rogue to make a Perception check to look for hidden things or an Investigation check to uncover or decipher clues as a bonus action. At first glance I interpret this as an extension of the Cunning Action feature (similar to the Thief's Fast Hands or Mastermind's Master of Tactics), by giving the rogue more things to do with their bonus action.
The Eye for Detail feature definitely has uses in combat. Bonus action Perception checks are an excellent counter against foes which like to hide (which my players face semi-regularly). Investigation is more situational, but not useless.
However, outside combat the action economy is not so important. If you are acting on the timescale of minutes rather than seconds it is not practical to track individual actions. But on the same timescale of minutes (rather than hours) you can, in principle, track things by individual actions.
By this reasoning, an Inquisitive Rogue can make twice as many Perception or Investigation checks in a given time-frame as any other character (assuming that is the only activity they are doing, and that the checks fall under the specifications for the Eye for Detail feature). They are able to search faster so, given a fixed time-frame, can search more thoroughly, or search a wider area.
Of course, I don't actually want to track actions round by round for a search which would take a few minutes. That would involve a stupid amount of die rolling and completely skews the statistics. But I was wondering whether the Inquisitive's Eye for Detail should still provide some benefit.
Would it be reasonable, under appropriate circumstances, to grant an Inquisitive Rogue advantage on Perception and Investigation checks outside combat? Or would this be unbalanced?
'Appropriate circumstances' being cases where simply searching more would plausibly improve chances of success (e.g. hide and seek), the timescale of the activity is short enough to make an intensive effort practical (but long enough to not be measured in rounds), the check pertains to the activities described in Eye for Detail, and the rogue is not dividing their attention between other actions.
My rationale behind this is that, in combat, a rogue can roll twice as many checks as someone else, so rolling advantage is essentially equivalent to that. I figure that a small circumstantial non-combat buff which emphasises the archetype's strengths is acceptable.
My concern is that this might be too advantageous. This greatly extends the usefulness of the feature by allowing it to be useful outside combat, and advantage is a large bonus. If this makes the archetype far more powerful than it should be, or has unintended interactions, then I should be wary about granting such regular advantage. I have not had much experience with Inquisitive Rogues; if they are a powerful archetype then such a buff would be unneeded, although if they are a weak archetype then this buff might be beneficial.
Note that I am not planning to explicitly modify the Eye for Detail feature. Rather, I will use my latitude as DM to grant advantage based solely on the implied usefulness of the Eye for Detail feature. But I wish to discern whether such a ruling is wise or unbalanced before setting a precedent.
Best Answer
This is crazily overpowered
Perception is the most common check made in most games, by far, and is used for uncovering clues, spotting danger and more generally gives the player information which allows them to overcome challenges more easily (i.e. you see a trap, now you don't take HP damage, life is easier).
Advantage works out to around +5, and also adds roughly +5 to any passive checks if you use those, because despite your saying 'under appropriate circumstances', it seems to me that it will almost always apply.
A +5 bonus to passive Perception is one of the key benefits of the Observant feat, so some people take an entire feat to gain the benefit you are proposing to grant for free. And if the feat granted +5 to active Perception checks as well, I think it would be even more popular because active Perception is amazing.
On top of this rogues already get Expertise, so if they care about Perception, they will already have a good Perception modifier, and adding advantage means they will notice pretty much everything.
It is important for the party to have someone good at Perception, but often this can be the cleric or a class with a good Wisdom score; what you are doing it making the rogue by far the best at spotting things, on top of all the other things the rogue is amazing at.
Other options
In a comment on the question, LizWeir suggested that this feature allows the rogue to multitask rather than making them better at searching. This could be represented by letting the rogue do something else at the same time as searching. I would go down that route if you want to provide a buff. And for what it is worth, I would not bother buffing this power; the player obviously liked the class enough to pick it in the first place.
You could do something like the ranger's Natural Explorer feature, which lets them keep watch while engaged in another activity while traveling for an hour or more in their favored terrain (the UA revised ranger's version of the feature works in any terrain). This would let the character keep watch while hunting for food or following tracks.
A word of warning
Giving a player a buff because of how they can use a combat ability out of combat may potentially make your other players get jealous (I would), and they might then try to find ways for their features to give them equally massive buffs. You would be opening up a can of worms.