You're Doing Tieflings Wrong

Tieflings do not have a standard skin tone, and 3e did not assign them standard physical features.

Look up Tieflings online in the D&D 3.5e SRD. "Many tieflings are indistinguishable from humans. Others have small horns, pointed teeth, red eyes, a whiff of brimstone about them, or even cloven feet. No two tieflings are the same." Note the use of the word or in the list of physical features, not and. And definitely note that the description reads "many tieflings are indistinguishable from humans". This is the full physical description and does not address skin color. This passage comes from the monster manual (where tieflings used to be) and the physical book provides an illustration of a woman who looks like an ordinary human.

For reference, even the description of tieflings in 2014 5e PHB, under the subheading "Infernal Bloodline" reads "Their skin tones cover the full range of human coloration, but also include shades of red." The red skin thing is new in 5e (or maybe it was 4e?) and it suits cambian demons, which are creatures with a human parent and an infernal parent like Hellboy.

In 3.5e, Tieflings are categorized with Aasimar under Planetouched in the Monster Manual. Quote: "Planetouched is a general word to describe someone who can trace his or her bloodline back to an outsider, usually a fiend or celestial." To reiterate, if you're a tiefling, you have a fiendish ancestor. That's bad. Here's why. Tiefling alignment is given as "usually evil (any)". The alignment of usually evil is the basis for discrimination against tiefliings. To quote 3e's definition of evil: ""Evil" implies hurting, oppressing, and killing others. Some evil creatures simply have no compassion for others and kill without qualms if doing so is convenient. Others actively pursue evil, killing for sport or out of duty to some evil deity or master." THIS is this the bases for discrimination against tieflings. Evil alignment in 3e is traditional black-and-white-morality, objectively bad.

Story Structure in TTRPGs

TL;DR, never call Act I an introduction. That's massively underexplaining what Act I is. Also, I worked out a really good reason not to play 5e D&D.

In story structure, Act I is the set up, Act II is the execution, and Act III is the resolution. 

In Act I, you set up the story. By the end of Act I, the themes, major characters, setting, conflict, stakes, and the goal should be established for the audience (or participants in TTRPGs). Act I ends when an event or action forces the hero (or by choice of the hero, but usually it's not their choice) to put their normal life on hold to engage with that conflict and pursue that goal. The number of choices available to the hero are greatest in Act I.

Act II is where you execute that story set up in Act I. If you set up a mystery, you execute the mystery, etc.  Act II is the longest act. Act II is about the hero engaging with escalating obstacles and risks in the setting as he pursues his goal. Obstacles (AKA trials) prepare the hero for their goal, first by testing the hero's skills and revealing his weaknesses or flaws, then by taking away his resources or nullifying his strengths, and by giving him lessons that make him stronger or wiser. Obstacles force heroes to confront failure; they force heroes to change or grow. Throughout Act II, minor characters and subplots may be expanded on or introduced, and are resolved before the end of Act II. During Act II, the hero's choices are narrowed down. By the end, the hero commits to one path. Act II ends when the tested and tried hero has overcome the obstacles and has learned from them, and is finally ready to confront the main antagonist.

Act III is where you resolve the story set up in Act I. It begins with a final confrontation with the primary antagonist that shows the hero's growth and how that growth made them worthy of their goal. Act III ends showing the audience the consequences of the hero's choices on the world; the world is not reset.

In good TTRPGs, Act I looks a bit like this: You ask the players what they want, give them some opportunities to get it, establish the obstacles that each choice will force on them, let them choose their preferred opportunity, then set them loose. I might even suggest working this into the ending of the previous adventure so that you start the next adventure with momentum. In D&D 5e, you pick one pre-written campaign book with a preset path and story.

In TTRPGS, Act II depends on the game you're playing. In 5e, you smash things, level up, gain powers, smash bigger things, level and gain more powers, and smash bigger things. Repeat until the second biggest thing is smashed and the players get some McGuffin. All while following a story that's already been written and is intended for general audiences.

In TTRPGs, 5e specifically, Act III is an obligatory fight with a damage sponge and a whole lot of cheap powers. Then you win the D&D. Seriously, why are you playing 5e? Stories are fundamentally about showing a character growing from a state of immaturity to maturity and imparting a lesson (a theme). Ever wonder why they call the moral of the story a theme? Stories are satisfying when a need for the growth is established in Act I, when the growth is earned through struggle in Act II, and when Act III reveals the results of that growth in a way that reinforces the lesson of the story. This character growth themes the story.

The Problem isn't the Experts

If there's a pool of knowledge, e.g. medicine or fry cooking, an expert is someone with a higher degree of knowledge (or expertise) compared to others who have general knowledge (subject matter generalists) or no knowledge of the subject (an ignoramus, used affectionately). 

I have a profession where I am considered a subject matter expert. I prepare data and information for others without expertise so they can make decisions. The decision makers can be other experts or generalists, or ignoramuses with or without competency in other fields, and they have the ability to reject your expert recommendations. They can instead fish for different experts who can provide them with a recommendation that they prefer or that suits the decisions they want to make.

The problem isn't experts; it's the decision makers who present the experts as authorities to substantiate their decisions. In other words, it's not a matter of whether we should trust experts or not; we should be cautious of the people who tell us which experts to trust. Everyone is fallible. Even the experts. Please see the two screen captures of both Bing results and Google results for the definition of fallible below and a very appropriate example of its use in a sentence.

The solution is critical thinking, more high-quality information, and waiting for the high-quality information to beat the low-quality information before committing to a decision. Recognize that not all decisions need to be made urgently. If someone presents a situation to you and requests a quick decision, consider the actual urgency and recognize that this might be a manipulation tactic. Have higher standards for proof. Ask questions. Make people show their work and don't take their word for it. Scrutinize it. Have others who are knowledgeable scrutinize it.