Cognitive distortion. This is a psychological effect that occurs in all people and leads to a distorted perception. In this case, we are additionally talking about the curse of knowledge, as the perceptual distortion is caused by pre-existing knowledge.
As a result, experienced people (and thus usually all the people who are active in the forum) cannot understand what the game is like for a true beginner or how it is played without prior knowledge. I belong to a larger group of players and have therefore been able to observe the difference between experienced DnD players and newcomers. And yes, the game theoretically provides all the information, but you still have to look it up yourself, which is more difficult than one might think due to the enormous amount of information.
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The second part of your message is very interesting.
You emphasize that "it's a PvE game" is not a good justification for poor balancing and that it should be the way the developers intended. But where do you get the right to decide what the developers intended? It was implemented in the game as it is, so that must have been the intention, right? And your example doesn't make it any better!
So, you want to take Tavern Brawler to fight with improvised weapons or to make use of them, which indicates that you want to fight with them. However, this should not work because thrown weapons and unarmed weapons become overpowered.
1. You are implying that improvised weapons are too weak since you can only use them if you have a feat.
2. Someone who wants to fight with improvised weapons will do so, so why would they fight unarmed? Throwing is such a specific action that most people probably won't do it.
3. The feat treats improvised weapons and unarmed attacks equally. Why, then, should unarmed attacks suddenly be so much stronger than improvised weapons? You must have mixed something up or missed some information because what you probably meant to say is that monks who focus on strength would become overpowered. And now to the next point.
Let's take Tavern Brawler and give it to a wizard!
OP?
We give it to a fighter!
OP?
We give it to a paladin!
OP?
We give it to a monk!
OP?
The answer to all these questions would be no! None of the mentioned classes gain an advantage from the feat without assistance. Wizards can't make use of it. Paladins, as far as I know, need a weapon. Fighters sacrifice too much, and monks need dexterity, not strength. Without equipment, the feat is unusable, and if you start nerfing because of equipment or equipment combinations, you could patch half the game into oblivion until everything is bad.
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Final point.
Another example I can't understand.
Yes, it's not a single-player game; you can play it in co-op. But please give proper examples, not ones that only apply to experienced players. How many beginners or regular players join a lobby of person XY to experience the story with someone they don't even know? How many who want to play the game want random players to join their game?
Your example is so detached from reality that it could come from the multiverse.
And if you're going to come back with the argument that you play with friends and it can happen there... do us a favor and save your time. Use that time instead to tell your friends not to play overpowered builds!
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Conclusion.
The mentioned issues regarding overpowered mechanics are a problem for experienced players who exploit game mechanics to become stronger. The combination of knowledge, knowledge, and more knowledge creates the feeling that something is too powerful, whereas it wouldn�t be too strong for an average player. Most players wouldn't even use the Tavern Brawler feat without the help of the internet. Similarly, strength potions, which can be easily obtained in the game, are consumables and are generally recognized by players as valuable, so they are only used when a battle seems difficult, even if the potion lasts until the next long rest. Furthermore, less experienced players won't breeze through battles as we do, so they will need to rest more frequently, making the "until the next long rest" effect less significant than for someone who can handle 6, 7, or 8 battles without resting.
A general tip for all players who believe they are good at something...
The moment you think you are good at something, you are no longer the benchmark for other players. This is why I do not see myself as a benchmark, as I belong to the group of good players in every game I actively play and engage with the game actively. While I find the game easy, think there are too few enemies, or that enemy X is too weak, regular players might struggle significantly to defeat that same enemy. As mentioned at the beginning, this is a cognitive distortion caused by the curse of knowledge. While it can't be completely eliminated, it can at least be taken into account.