good conversation...
As I've considered things more, I think it does make sense that certain things are worth less at higher levels. As such, I could buy that each point of XP was worth less amount of CR. An example of this is that the Orc's aggressive quality has a higher impact on a creature's CR when added to a low level creature and less impact on a creature's CR when added to a higher level creature. Though, if that's the case, I'm not quite sure if there is a defined way of figuring out how the math changes.
It makes sense that different tiers of the game should be faster or slower as well. No confusion there, and that does give some insight on things, but I feel as though that may be an independent issue. Leveling speed could be adjusted by changing the amount of XP needed for each level, but, while related to my original questions, it's currently outside of what I'm looking at. (Though don't take that as meaning it shouldn't be discussed.)
Part of my increased interest in how XP values for critters of different levels are determined is based on a few different things. First, as said, the math doesn't have a clear pattern which I've noticed (but that's been somewhat answered by input from others). Secondly, as I've been perusing the forum, I've read multiple threads in which certain monsters are said to be either too easy or too hard for their given level, and I'm curious if perhaps that's because -by the raw numbers before adjusting for "tier speed"- they are. Thirdly, while 4th Edition certainly is not my favorite game (as is obvious by some of my posting history), I do think that 5th Edition monsters could benefit from some of the concepts seen in 4E; one such concept was the idea of "elites" being better than typical monsters of their level, but not quite boss monsters.
The first, as said, has been talked about and is leading to some interesting conversation on the topic. The second is something of which I am still unsure; I have opinions from a player pov, but my time as a 5E DM is minuscule. The third is something that I think could be done with my half-CR concept (but only considered while typing this post.)
So... 5th Edition "Elites"... [warning, this goes off on a bit of a side-conversation]
I think legendary actions and lair actions are a great idea. It's one of my favorite parts of 5th Edition, and it's a more codified version of something I had started doing toward the end of playing 4E to make Solos better. (Side note: I recently started playing in a 4E game, and the DM for that game has started adding 5E style legendary actions and lair actions to 4E Solos, and it has helped a lot.) I think adding a lesser version or perhaps fewer of the same things to a normal creature could make for an interesting sub-boss during an adventure. You might also be able to go the opposite way and steal a few tricks from 4E to make a monster a little bit tougher for one encounter. Some examples below:
Smaller Amount of/Lesser 5E style legendary action(s): Once per round, a particularly tough Ogre can -as a free action- try to stomp a PC who has been knocked prone and deal extra damage.
Adding some 4E stuff to a 5E creature: Perhaps the some hypothetical Ogre could be given an additional +2 to a save and one "action point" which it can use to take an extra action once per encounter.
I dunno... just a thinking as I type.
[getting back on track]
At any rate, as I've already said, I've come to realize that a lot of creatures I create myself tend to not neatly fall into the range of CRs. I quite often end up with creatures that fall somewhere in between. As said, most often, if it's at least close, I just round things off. However, occasionally, if something seems significantly tougher or weaker, I make it worth a little more or a little less. I also feel that some things (like a creature's speed, movement modes, and special senses) often do make a creature tougher (despite the rules of the game saying they do not) and using values between CRs can be a way to fine tune things when I think they matter. Ideally, if I start sketching out the "elite" idea, I'll likely aim for most of them to be at the half-CR marks.
At the same time, some of the insight I'm getting from this conversation and looking at the math related to it has given me some insight on designing traps (which is an area that I feel 5th is a bit more empty and boring than I'd like when looking at the DMG).
Things I'm learning from this thread: I thought I was supposed to multiply the rewarded XP when using multiple creatures. I didn't realize that multiplication was intended to only be used for gauging difficulty.