Reading the "details about your specific game": your game doesn't seem "too hard" to me. It doesn't seem that deadly. It's probably challenging, but that's not a bad thing. Lots of players enjoy the challenge and would be happy to play in such a game. Even players who casually complain about difficulty may enjoy the challenge. I would know, because I tend to do that: during in a hard, really tense fight, I tend to not enjoy it that much at the time, and even complain about how "my god, that monster hits so hard, it's unfair, the DM's out to get us", because I'm afraid and stressed I'm gonna lose my character. But once the fight is over, I'm happy about how epic and challenging it was.
If that's not the case for your group, though, and if you genuinely think you should dial it back, I'd go with that third one:
Quote Originally Posted by Talakeal View Post
3: I might just play monsters too smart. I typically allow them to use tactics, prepare for the fight, and make use of the terrain. For example, I remember back in the college gaming club being sad that the other DM always had more players, and one of the guys who was in both games said people came to D&D for big dumb fun, and compared a fight where he had an ancient half shadow half fiendish red dragon with class levels charge in and brawl with the PCs, while I had a standard young adult green dragon use cover, camouflage, deadfall traps, and low level buff spells, and both were able to be of a similar level of difficulty to the party.
Yup, that's probably it. Monsters of the same CR are not equal in difficulty, and a monster may not even be equal to itself depending on how it's played. As a DM, I notice that the more effort I put into building my fights, the harder (and also more dramatically tense) they tend to be. If I think a lot about how to build a boss fight, if I prepare tactics, etc., the way you do, the fight is harder. If I just roll a random encounter and pull the monster straight out of the book without analyzing its stats block and playing to its strength, PCs usually steamroll the fight.