+18? Something still isn't right.
Charisma 20 =+5
Proficiency Bonus =+2
Performer Feat =+2 (double proficiency)
Expertise = x2
5+2+2=9x2=18
Sent from my iPhone using EN World mobile app
+18? Something still isn't right.
Charisma 20 =+5
Proficiency Bonus =+2
Performer Feat =+2 (double proficiency)
Expertise = x2
5+2+2=9x2=18
Sent from my iPhone using EN World mobile app
Charisma 20 =+5
Proficiency Bonus =+2
Performer Feat =+2 (double proficiency)
Expertise = x2
5+2+2=9x2=18
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Yep, there is the problem.
The correct calculation is: 5 + (2×2) = +7
Expertise only doubles your profiency bonus. "Your proficiency bonus is doubled for any ability check you make…"
The Performer feat does the same. "You gain proficiency in the Performance skill. If you are already proficient in the skill, you add double your proficiency bonus to checks you make with it."
If you have multiple ways to add or multiply your profiency bonus, you only get to do it once. "Your proficiency bonus can’t be added to a single die roll or other number more than once. For example, if two different rules say you can add your proficiency bonus to a Wisdom saving throw, you nevertheless add the bonus only once when you make the save. Occasionally, your proficiency bonus might be multiplied or divided (doubled or halved, for example) before you apply it. For example, the rogue’s Expertise feature doubles the proficiency bonus for certain ability checks. If a circumstance suggests that your proficiency bonus applies more than once to the same roll, you still add it only once and multiply or divide it only once. "
If you have the Performer feat, then taking Expertise in Performance is wasted.
Additionally, the GM always has the option of just saying "no". The rule of the game is: (1) Players describe intention and approach. (2) GM decides success, fail, or uncertain. (2)(a) If uncertain then roll dice. (3) GM and Players narrate the outcome.
Sometimes, it doesn't matter how persuasive you are, the person just can't be swayed. Might I suggest intimidation or bribery instead?
Finally, two bards with excellent diplomacy sounds like lots of fun! Imagine Han Solo and Lando Calrissian in the same group. Watch Oceans 11 and see how having several suave, smooth-talking charmers doesn't hinder the plot at all. Two bards sounds to me like the players want some cool caper-style adventures.