Hello everyone 
My friend Vanquished and I have been analysing in-depth KTera videos from this new 20-Man revamp to write a guide as complete as possible for everyone to be prepared and plan their raids. Guide is targeted for both rookies and experienced players and we've split the content in Old Mechanics and Modified/New Mechanics for easier navigation.
You can access the Google Docs file here: https://goo.gl/b9ZwLM
Credits to multiple individuals are given inside the guide, but we want to specially thank GalGoRi for his 20-Man videos in YouTube that have been the base for this guide and the EssentialMana team for their help and support.
If you guys have any missing information we could add in the guide it'd be great if you could let us know!