To the OP with all due respect, it’s kind of the point to go in knowing nothing and having to figure out how to win.

That said, could things be better? Yes. Specific markers are very sloppy pre Heavansward (gather together, run away, etc often just used generic orange/blue with no continuity across fights).

That said, if you play the game you will find certain mechanics introduced either earlier in a previous dungeon as part of a boss or in the case of trials, often the first phase previews different mechanics. The new Eden 2.3 is a great example of this.

In addition, bosses for a new expansion tend to use mechanics from the previous expansion’s raid series (eg. A certain tentacled boss in a certain undead themed flying ship has been reskinned in both a Heavansward dungeon and not one, but two shadowbringers’)

Allllll that said, if you are overly self conscious of dying I highly recommend MTQcapture’s guides for a quick and dirty before going in.