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In my experience, the rarer the card(s) that produce a token are, the rarer the token.
So if a token is produced by only one mythic in a set, it's probably only on the token sheet once (1/121 odds) If a token is produced by only a single rare, it will be on the token sheet a few times, etc. Exceptions are made later in the block, where a previously common token stays common, even if it's only producer is rare.
Compile a list of what cards make what tokens, and their rarities, and you'll have a good feel for the tokens' relative rarities.
Edit- doing a quick search, the Dragons should be the rarest from WW and ARB, and the Angel in CON
At a guess, Eventide would be 5/5 U/R Elemental (Call the Skybreaker), would it not? 10th would almost certainly be the 5/5 R Dragon from Dragon Roost, and I'd guess WWK would be the same, from Dragonmaster Outcast. There are no obvious ones from Conflux or ARB though, at least not obvious to me.