I genuinely don't think it's possible for me. I've tried hundreds of times, I'm getting stunned OUTSIDE of red AoE circles, and I can't get the boss even close to finished before the 1st CG spawns before the crystal stage. It ALWAYS spawns. My damage is high enough, I'm applying my DoTs and weaving attacks, still running out of magicka and getting 1 hit when no shields are up.
A. I DO need my shields up, surge isn't healing enough to keep me alive. B. My damage is very high, but somehow not high enough to make the boss go up before the Daedroth spawns. Likewise for the after-crystal stage, daedroth spawns and I get destroyed.
This arena is a joke, honestly. Most of the time I find that the issue IS unresponsive controls and weird bugs where I'm getting hit and stunned when I shouldn't. Like I said in my OP, I've played Dark Souls, and even that's not as stupidly difficult as this, OP maelstrom weapons included or not.
I hate to break it to you but your damage isn't very high if you can't burn the boss to 70% before he teleports. I do it almost every time with mediocre damage, stamina or magicka. I do remember what it was like to feel the way you do. Feeling like RNG was hosing me, but the fact is there's no RNG in this fight besides where the boss teleports to, which can easily be neutralized by attacking the boss boss from range while going to the gold ghost.
As others have said, this is one of the easiest boss fights in the arena after you've done it a few times. I say this as someone who died more times on the last boss (about 200 times) than I did the entire rest of the arena on my first clear.