This was Elite with a melee build without dot dmg.
The doombolt warning pool can be hard at times to see amongst his black goo, however it can be impossible at time when it spawns them more under him than you.
This is the 2nd phase.
Even being aware the doombolt pools occur, I was surprised when at least 2 hit me because I just could not see them amongst my animations-Beronaths, and crucially the dark goo around us when fighting close.
Trying to lure him out of the goo is time consuming and usually I just ended up with even more goo over the arena - not sure if there is some RNG in how often he uses this effect.
For a range or mostly dot build in my experience its not an issue and the fight is pretty comfortable.
I just feel we need better indicators for when all of these are happening together in close combat, with maybe more timing gaps between certain Beronath skills.
Edit:
Just to say the comment was more relating to the 3 pools, rather than the consecutive multiple ones.