True, but I think better/ more accurate guidelines could be helpful. That is what I am trying to work on.
At the risk of sounding like a broken record, I think you're making a mistake here.
I've talked a lot on a couple other posts about why CRs are determined the way they are (that is: only considering damage/hp, and ignoring versatility, even when versatility can
massively impact a fight) and I think that the XP thresholds are, similarly, also determined a specific way intentionally.
XP Thresholds
aren't for you.
They aren't for any of us, really. I'd hazard a guess that the majority of people who care about D&D and think about D&D in their spare time so much that they feel compelled to post about D&D on a web forum are categorically
not the people the XP thresholds were designed for.
So of course they will seem woefully low to you. Because they're designed to assist casual/novice DMs who need help getting a quick-and-dirty handle on how difficult an encounter is going to be. They err on the side of too-easy... because casual/novice players are often
orders of magnitude less effective than experienced players.
I guess the logical response to this is "Okay, so, if that's true... all the more reason to create a new threshold for experienced groups!" Which might be true. Except that CR... you know, the thing that determines the XP values themselves... is calibrated the same way.
So XP values are not remotely a reliable metric for how difficult a fight will be, overall. 6 goblins can be much more deadly than an ogre, if run by an experienced DM utilizing brutal tactics against PCs that also utilize good tactics.
So any threshold you care to make will not actually be the tool you want it to be. The only way to have that tool is to redesign CR from the ground up and try to take into account every bit of tactical flexibility a creature has.
And... I don't think that's a feasible task. Though I have 20+ years experience DMing, I'm still confident that the amount of tactical flexibility I will wring out of my monsters is not the same as what [MENTION=6787650]Hemlock[/MENTION] will be able to manage, for example. Such discrepancies, on a specific level, will occur over and over between each of us. You simply can't take every variable into account in a codified system that way.
So instead, CR is based purely on the monster's damage capacity, taking and receiving. And XP Thresholds will always be rough/loose approximations. Any truly seasoned DM is going to do one of two things:
#1: He's going to build his encounters with acute awareness of the monster abilities and tactics he will use, and his party's ability to overcome those. He will craft the encounter to be precisely the level of challenge he wants, irrespective of CR and XP Threshold.
...or...
#2: He's going to populate his world with the monsters and NPCs that make sense. The party will find them as they exist, engage with them on whatever terms occur in the story, and whether or not the challenge is easy, deadly, or a TPK will be something the table figures out together. CR will be useful to find out how much XP they get after the fact, and the thresholds won't enter into it at all.
I appreciate your quest. It's a noble one. But I think it's never going to yield the results you want.