Inquisitive (Homebrew)

Inquisitive rogues are experts at uncovering secrets, detecting lies and falsehoods, and rapid analytic thinking. They excel at rooting out those who prey on innocents while masquerading as upstanding citizens, or those who rely on stealth and trickery to commit crimes. Their senses are sharper than their blades, and they are experts at reacting to and exploiting an opponents mistakes to strike their weak points.

This is a homebrew update to the Inquisitive subclass found in Xanathar's Guide to Everything and aims to address a number of mechanical and thematic weaknesses I believe held the subclass back from fully realising it's potential.

Ear for Deceit

When you choose this archetype at 3rd level, you develop a talent for picking out lies. Whenever you make a Wisdom (Insight) check to determine whether a creature is lying, treat a roll of 7 or lower on the d20 as an 8.

Quick Mind, Sharp Eyes

Starting at 3rd level, any Wisdom (Perception) check or Intelligence (Investigation) check you make in combat, for example, to spot hidden enemies or uncover clues, can be made as a Bonus Action, rather than an Action. If the DM decides any of these checks would be a free action, they remain a free action instead of becoming a Bonus Action.

Exploit Mistakes

At 3rd level, your keen eyes allow you to quickly react any time an opponent's guard is down. If an enemy within 30 feet of you that you can see misses an attack roll against you or an ally, you can immediately use your reaction to make an attack roll against that enemy. You add your Wisdom modifier to this attack roll. Additionally, unless you have disadvantage on the attack roll, this attack always counts as a sneak attack.

Know Your Enemy

You are able to quickly analyze a target creature and pick up key details about its strengths and vulnerabilities. As an action, you can quickly study a target creature and learn crucial information about it. You immediately learn the following attributes about the target: Damage Vulnerabilities, Damage Resistances, Damage Immunities, Condition Immunities. You can use this feature a number of times equal to your Wisdom modifier (minimum of once), and you regain all expended uses of this feature when you finish a long rest. 

Razor Instincts

Beginning at 13th level, your instincts are so honed that it is almost impossible to fool you. You automatically sense the presence of illusions, shapechangers not in their original form, or other magic designed to deceive the senses within 30 feet of you, provided you aren’t blinded or deafened. You only sense the presence of these deceptions, not their precise source or nature.

Additionally, you gain advantage on any Wisdom (Insight) checks to detect if a creature is lying.

Eye for Weakness

At 17th level, you make your enemies pay for every gap they leave open for you to exploit. If you hit a creature with an attack using your Exploit Mistakes feature, the Sneak Attack damage against that creature increases by 3d6.