I'm trying to help an OS kitty reforge for RoR with Catus coming from Zephyrus it's WAY more complex and intimidating, and someone told me they go for haste, but it seems to be set up for only Mastery.
Could you describe your problem? What exactly is "WAY more complex/intimidating"?
In general, if you can use Zephyrus, you can use Catus. They function exactly the same, just Catus is a bit more spread out, as reforging is not the primary purpose.
With the defaults, it should take just a few clicks: reveal the Import panel, enter your characters name, click "Import", reveal the Reforge panel, click "Reforge". You have the same options that Zephyrus provides. If anything, Catus is easier because: 1. Feral reforging is faster/simpler; and 2. you have a paper doll, gem/enchant listings, and full gear auditing with warnings.
"Compare to Armory" can be found under "Gear Differences" panel.
Going forward (assuming you're using the latest version), you can trust that Catus and Zephyrus are making the proper suggestions for your character. For example, while it is easy for the 1:1:1 reforger to favor Haste or Crit, I don't even present this option because it's unnecessary and confusing.
Catus has two additional benefits over Zephyrus in regards to the Rune: 1. it gives you notification that you're wearing a rune; and 2. the text that describes your current proc amount will be green if it's mastery, and red if it's crit/haste.