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

[Daeriion_Aeradiir]

A good example of this is the fire/ice arrow "maze" on the fifth encounter. Just looking at it the first time, I had absolutely no idea what was going on (I'd read a strat before entering, but wasn't clear on exactly what I was supposed to be doing).

What? The arrow maze is arguably one of the most telegraphed mechanics in that entire instance compared to other mechanics you could have mentioned. The very first time I saw it blind, I knew instantly what to do based on all the info it gives you:

-The arrows on the opposite side have the gauge indicators, and you experience at least one hot & cold before the arrows so the temperature gauge isn't new, so by this point if you died to the first set of hot & colds, you should understand the mechanic is based on these temperature gauges.
-The maze traces the route the arrows will be taking extremely blatantly with a white line starting from each start point and reaching its intended end point, which even if you don't immediately clue in that the arrows will always turn if they're able, still shows you the exact solution to each of the two arrows.

The next arrow maze adds the ^^ & vv temperature arrows, but the previous hot & cold also introduces the concept of the 2x temperature gauge so its literally just the same as last time, only you find the 1 arrow's white line out of 4 instead of 1 out of 2.

There's far more egregious 'gotcha' mechanics in Delebrum, like the Crocodile instantly cleaving the other half of his side right after the first hit with zero indication, Trinity seeker's full room aoe just making you have to guess you have to hide behind a wall, or the rings being a 50/50 chance you get hit the first time you ever see it since there's little visual indication. Arrow Maze is one of the easiest to understand mechanics on the first go around with how much info it gives you.