In this thread Kyronix said it was all RNG.
https://forum.uo.com/discussion/comment/112335/They could have turned it down since that post, who knows, but with probabilities that low, you can get long streaks without a success even without them turning it down.
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Pretty sure we all already know the answer to your first issue above. They are not going to reveal the spawn rates on anything. If the players knew precise numbers, it would open a whole can of worms with manipulation of the design.
Also, not revealing the numbers gives the devs fudge room, so that they
can adjust stuff on the fly, as needed, or as they see fit. If we notice, they can just say "RNG" folks, with a wink emoji.
I suspect the best we can hope for is a definition of common, uncommon, etc., and that the team is consistent with those definitions so that we, as players, can kind of get an idea of what to expect.
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As for the base vs. totem values, that's going to be part of the design choices they are looking at. Are they building a system around individual players, with chances designed to reward an individual, i.e. 1 : 10 drop rates, or are they thinking about the number of items entering into the game world as a whole, and drop rates are set to keep things limited overall, i.e. 1 : 10,000? Below is a layout just to highlight that concept. (There could be any number of rarity models, including middle grounds, or even more extreme rarity, i.e. 1 : 100,000 or 1 : 1,000,000.)
A 1 : 10,000, or 1 : 20,000 drop rate seems crazy, until you remember UO is an MMO. It's not just you, or I, looking for rares. The numbers the dev team see are probably nuts. Let's just do some very broad stroke math.
If you're balancing game wide, you start out with what appear stupidly low drop rates. The aggregate of all those players playing all the time adds up fast though, and even a 1 : 10,000 drop rate produces 100's of "uber rare" items.
Now bring in the totem. Which type of rarity model, what type of metrics are they considering for game balance? It looks to me the rarer mares are extremely rare, say 1 : 5000 or 1 : 10,000 without the totem, and the team is looking at a more game wide balance/rarity. Technically you could get one without a totem, but that's a lot of game time. That totem is probably giving you a significant boost, so that as an individual you have at least a more realistic chance to tame a rare, even with the base rarity set to a stupid low MMO model.
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As I said before, good luck to everyone hunting rare pets!
I don't do the pet thing and haven't tamed a single mare. I was just interested in what the rarity models behind the scenes might look like.
Have fun all!
