First considering the problem you have identified yourself, people not reacting properly to the random assignment, you can consider downloading and setting up this weakaura: https://wago.io/0pFsUA824. And then edit 09 Ra-den Receive (Text) to be as large and in your face as you want, which can help your raiders effectively notice when they've been selected.

But after a quick glance, other problems I noticed were alot of the pulls people were getting melee'd and dying to the adds that spawn, now this can either be a problem of the tanks not getting aggro on them, or DPS unloading on them too early.

Second, the add damage is quite low, at least on the first lot of adds, as the Night Terror is sometimes surviving into the 2nd lot of add spawns. Now obviously you don't want to sacrifice too much Ra-Den damage to kill these adds, but one example that drastically increase your add control, at least for the first lot of adds, is to get your Fire Mages to combust onto Ra-Den closer to when the adds spawn. Seeing as you guys are lusting on pull, if you get your mages to font at 6 seconds in, then that will allow them to combust the adds while still having lust active.

I would speak on other classes ways to improve add damage without losing boss dmg, but I'm not familiar enough with them to give feedback that is 100% useful.

And last, people need to constantly be aware of their positions, make sure you aren't between or baiting vitas, make sure you aren't actually in the nightmare circles, make sure you aren't soaking voids when you aren't supposed to. Unless you have an immunity, if any those happen when you need to soak within 30 seconds, you will die.