You can parry the beams with any type of shield...
This dude is doing it at the beginning of the game with a weak as goblin shield
I am doing it now not even using a shield I am using a cooking pot lid as a shield
The problem is you either do it right and deal half damage...
Or you do it late and it hits your shield and it will evaporate the shield...it does not matter what type or how strong the shield is...it can be a guardian shield you parry and swing to late and miss and it just hits the front of the shield it will evaporate it
Or you parry to early and get hit by the beam and either the beam outright kills you or it hits you and you fall and it just keeps hitting you until you die...
So you either parry and do half damage...parry to late and lose shield...parry to early and die...
Now you CANT parry the beams they do when they spin in a circle and the beam arc keeps going out...you are supposed to use the draft from the beams to fly up and arrow them slow motion in the eye...
I don't know if you can parry the short 3 round laser burst they do when you are up close...that attack is not telegraphed...I tried twice today but I was very late so I got hit both times...
I can't even imagine fighting those level 5 guardians without parrying lasers
...they have 3000 hit points
...my rake and travelers sword surely won't last that long