Assasinate change

[clash]

The Assassinate rogue ability has always been in a weird place. Theory-crafters love it a little too much and in practice players are not generally satisfied with it. So I am proposing the following change to fix it. Please let me know if it seems balanced and/or how to improve it.

Assassinate
If you are hidden from a creature, you can use your action to study them to discover their most vulnerable point. You must make a Wisdom(insight) check contested by their Cha(Deception) check. If you succeed then the next time you hit them with an attack roll, it is automatically treated as a critical hit.

[Lalliman]

I don't know about the balance, but the choice of skills is a bit odd. Insight is for social situations, not for spotting physical traits, and how can you deceive someone if you don't know they're watching you? I would suggest making it a Perception or Investigation check against their AC. It's probably more balanced that way too, since many enemies have a non-existent Deception bonus even at high levels.

[clash]

Ya investigation seems good actually. I don't like ac in that it seems nonstandard to make a skill check against ac. How about dexterity(acrobatics) as a representation of how predictable their movements are?

[Lalliman]

It is non-standard, but the numbers will match up better than with an opposed check. A skill check is equivalent to an attack roll in terms of the numbers it generates (d20 + stat + prof). Expertise theoretically skews the success chance in favour of the rogue, but in practice it will probably do little more than make up for the rogue's middling Intelligence score.

By comparison, making it any kind of opposed skill check will skew the roll in favour of success because few of the creatures in the Monster Manual have skill proficiencies at all. It will also be highly polarised, with a small amount of creatures being unexpectedly resistant to it simply because they happen to have a good bonus to that particular skill, which likely has no correlation to their actual power level.

Additionally, someone's armour should also have a say in how easy it is to find a weak spot, not just their agility as with Acrobatics.

Thus, I stick to recommending AC.