when youre in a safe spot only move if you absolutely have to, usually that means only move when the beam is so close it could burn your nosehair.
I dont know how you call it in english but I found that in maze phase it helps a lot when you're looking at your character from straight up above (birds eye view?). it helped a lot in the zorlok heroic fight, it helped a lot here as well.
I found the opposite better for myself. Staying at the outer edge of the free spots, staying as far away from the beam as it's possible so I can have time to stop and cast.
It can be quite hard to see. But after some time you should have a good idea of where the open spaces are even if they're hard to see. This is really only a problem in melee range tbh. if you get the open space virtually under the boss, you will feel like you're just about to get hit by the beam before another tiny space opens.
Keep in mind that spaces don't open up until the beam is getting pretty close to you. I think one of the mistakes people often do is that they see the beam of death is very close to them, and they panick and move away from beam and into shit on the ground.
I tried all kinds of different settings to help see the effects better and the only thing I found that really helped was turning the gamma way up. The normal setup is pretty dark and dark purple spell effect makes it very hard to see what is happening. Last night I turned my gamma way up, the game looks a bit washed out but during the eye maze phase the path becomes very clear to see.
Seriously what worked very well for my raid was stacking at max distance initially (the very end of the purple squiggly thing that marks the side that will be initialy open) and mark oneplayer that can certifiably see the maze and know how to manouver his way arround (mostly me our hunter or our priest) and follow him. Worked like a charm.
Easiest way to do this is to stand in the bosses nuts, and only move as the beam is about to hit you. That is the only location that is consistently safe through the kills I've done. Also, blow healer and defensive CDs at the start to help mitigate while everyone gets situation.
The most important thing is to not panic, and stay stacked up. The closer you are to the beam without touching it, the safer you are.