Not sure if you're doing something wrong or just suck at dodging attacks...
I first started soloing hard Gollux with only 300kish range on my shade, and that only took 15 mins. Now I got twice that and I can solo him in 5 mins. You probably just suck at dodging his attacks. I'm not sure if you can snipe his chin like how night lord does, but if you can then make sure to take out his right shoulder if you're going against him. If not then take out his Abs and use beam dance.
Then when you get to the eyes go to the top left platform and go to the left of that platform so you can avoid all the attacks he throws at you during the eye stage of Gollux and make sure to use snipe for this part.
Then when you're at the forehead use beam dance like no tomorrow
And make sure that you place that DoT skill with the ball in the cube or whatever it is on the floor so the mobs don't touch Gollux and kill you.
Once you get the timing for Gollux down he's easy.