Most of the cues seemed to have been designed on the idea that the player would be able to easily see their character, or hear things very clearly. Take Crystal Fragments, for ex. your hands turn pink, your skill icon changes, and there is an audio queue. Or merciless resolve, you get an audio queue, and your skill icon changes. Or Llothis has me targeted for cone-vomit... i glow green and/or get a small target marker on my feet.
Here are the problems with that:
I usually have 3-11 people stacked up on top of me. I can't see if my hands are pink or if I am glowing green. I also cant really see a marker on my feet very easily. I can't hear audio queues because 12 people are grunting and shouting while stuff explodes, etc. and a bunch of people are probably in voice chat.
If you want me to look at my skill bar icon all the time, or try to track buffs and debuffs out of those dozens of shifting squares... uh... that's (a) not fun, (b) not immersive, and (c) not practical, because I have to keep track of mechs by looking at whats going on, not staring at a HUD.
My Suggested Revision
Use the screen border and screen tinting A LOT more for telegraphing these queues to the player.
Merciless Bow proc... gimmie a border that intensifies on 3, 4 and 5 light attacks.
Crystal Shards... maybe a pink border or something?
Llothis type targeting - tint the screen green? Or use some other kind of screen border.
Also...
I've already said this a billion times, but all those shifting squares for buffs and debuffs are horrible GUI.
Copy how the addons track the DoTs and Buffs and make that a part of the Base Game PLEEEEEASE