I don't know where you were looking, but I suggest you buy a copy of ERIC II:
There are many great sources to search online. Other than this site, some of my favorites are:
Regrading rarity, you need to take the ratings with a grain of salt. Especially for bronze coins and even more so for coins of Constantine and later. The rarity ratings are based on examples in museums and published collections and were compiled a long time ago. At that time, bronze was not actively collected, so there were fewer coins included in the rarity statistics. Additionally, the Balkans opened up to the world after these ratings were published and many more bronze roman coins flooded the market.