iserith
Magic Wordsmith
I can honestly say you are too confident. I've played in your style before. I've done it. Honest. I've given it a whirl and I'm not interested.
Just as a comparison, in my last session, 3 hours and we ran 4 combats, 5 social interactions and several explorations. Granted the characters are only 3rd level, so that makes combat faster, but, this is also online over voice, which is almost always slower than tabletop. Just for reference, I'm doing the tail end of Chapter 3 (____ Manor) and the first two encounters of Chapter 4 of Dragon Heist (Autumn). Oh, and we leveled up characters in the middle of that.
So, no, you can be as confident as you like. I am equally confident that no, you are not running at our pace.
My last session included 5 combats, 6 separate exploration challenges, and 3 social interactions in 3.5 hours over Roll20 and Discord. The characters are 5th level. It included one PC leveling up mid-session. (The others leveled up at the end of the previous session.)
Asking players to perform their role and responsibility in the game (and the DM doing the same) does not slow the game down by any great degree.
So, here is a list of my issues with your style of play and why I don't do it. Note, this is purely my opinion and is not meant to apply to anyone else but me.
Changing DC's based on player statements results in the players not being able to predict how their skills work. @Ovinomancer's example of the poisoned door is a perfect example of that. The results I get have nothing to do with the skill I use but rather whatever narration I give as a player. Which in turn, results in gaming the DM rather than playing the game.
Skill proficiencies work as expected - as insurance against failure when you fail to achieve outright success. The goal is to remove uncertainty as to the outcome and/or the meaningful consequence of failure. If you can't do that for whatever reason, then your abilities and potentially skill proficiencies come into play.
You're not gaming the DM here. You're paying attention, engaging with the environment, and trying to mitigate risk by avoiding rolling a fickle d20.
It places the DM squarely into the spotlight. Since the DM must judge the quality of the narration (is it plausible or not, is it a good idea or not) and that judgement is based solely on the DM's knowledge, it makes the DM much more visible than I'm comfortable with as a DM. I don't want my players asking me how to do something. I want them to just do it.
We're performing the role of the DM as described by the rules of D&D 5e. I don't know what you mean by players asking the DM how to do something. My players take action. They don't ask for my permission.
Many DM's, myself included, are very poor at judging risk/reward. If the reward is less than the risk then there is no reason to do it. Yet, almost every time, DM's will put risks in place that are greater than the possible reward, making it a suckers bet. Which in turn results in the players simply stopping engaging those systems in favor of systems that they can control - i.e. spells. It's something that always flies straight up my nose.
You don't get better at something by not doing it.
And, with all due deference to @iserith, it runs too slowly for my tastes. It bogs the game down in minutia that I am totally not interested in. I don't care that there's a contact poison on the handle of the door. I want to know what's behind the door. To me, that's the interesting part. So, bypassing the trap as quickly as possible is a win in my books. Resulting in the player saying, "I check the door, X Investigate, do I find anything?".
It's not any slower. Or at least my game's not.