The mechanic seems simple, but there was just tons of damage coming out. It's possible people weren't running out of the circle quickly enough, but I didn't notice people continuing to stand in it, and I don't believe they were undergeared.
We wiped twice, and then easily killed him when standing behind the crate. Two pulls certainly isn't a large sample size, but fighting that boss legit is the only thing that I have perceived to be difficult.
To groups who have trouble doing it the 'legit' way, I encourage you to try it as intended:
With Force Speed you can get out of the circle before taking a single tick. I did it on a 58/61 geared sage. With Transcendence you can get out with only one tick, which is more than manageable. Hunker down also works here. Scamper works well. A guardian could Guardian Leap to a gunslinger. I'm not sure if the circle is force or melee damage, but either Resilience or Dodge will work. There are a myriad of ways to minimize the damage. The timing between pulls is very consistent, so you can pop a defensive cooldown or throw out bubbles preemptively. After it's over, ball up for a group heal. This is all basic stuff if a group plans to do further content, especially operations. Learn it here in a fight that is otherwise very simple.
I was astonished to see people complaining about this boss. Yes, if you don't notice the circle or get hit by too many ticks the fight will be a problem, but that's the whole point. I don't like the idea of exploiting this fight because it's a very common mechanic, and many fights that are much more difficult have something similar. If a group can't do it here, they'll have trouble elsewhere too.