DaveW - Leviathan is a promo card that through testing most players agree for an official release needs some balancing before it is allowed in a tournament setting. Most errata is in a situation where through years of tournament games have been proven to be too powerful. We aren't doing many changes to officially released cards in sets, and the ones we are doing are with thorough testing and community discussion. Keep in mind the Wizard's Tower errata is not a part of this set. That was done back in 2016. Most of the released cards that are receiving an errata have been on the docket since 2017 (Zombie Brute, Pillar of Righteous Flame, Disciple of Radiance, etc.), and are now being taken care of.
Graf! - Welcome to the community! I know there are a lot of cards to go through as this is a massive game. OCTGN right now has a Final Release section. The goal of that section is for all promo cards that were unreleased to be released. As a rule use those over the previous Promo section (which served for promo cards that were not included in a set). It is in a public playtesting phase so they will be subject to change (although 90% of them have been this way since the start of the year). We will probably have another tournament to sometime in the Fall using these new cards on OCTGN. We would love to see you there!
