Delubrum Reginae is the best raid you've designed... BUT...

[Vahlnir]

but I probably died 10 times on that first run. And this is because it's perhaps the worst content SE has ever added to the game when it comes to teaching mechanics.

Did you ask anyone how they worked? If you don't want to do that then figure them out yourself. If you don't want that either you can always read or watch a guide. I died a lot in my first few runs too (probably more than you) but eventually I picked up on these things. In my opinion they aren't hard to deal with once you know what's what. I'm a casual player by just about every standard. It's fine as is on this front. They teach you the mechanics through trial and error. Not everything needs to be displayed in big, bold letters on a flashing neon sign which reads "OMG STAND HERE NOW!" (The game already does that by the way in most parts of the game). There is nothing wrong with having to use one's brain a bit. I'd argue that it is actually quite healthy. lol