Boss in A Moment: Whole is unkillable

[RoaringTides]

My fiance and I were doing a run on drizzle, just for fun. Got Beads of Fealty and went to A Moment: Whole. Got the scavenger variant with Shattering Justice, and every time we got him down to 25% hp he got right back to full health. Blasted him for about 30 minutes or so before giving up and just quitting. Kind of a lame way for it to happen too, since it was our first time going there. Can't really help but feel like this is not intentional, as it completely soft locked the game.

[NuclearPoweredBadger]

I've killed him, on monsoon, really easily. Try different tactics rather than running at it. There might be a reason the level is so large.

[RoaringTides]

Wow! What an abnormally unhelpful response! Glad to know you had such an easy time with the boss, you're very good. Thanks for the feedback!

[Nada Afterwards]

Guragura has spinel tonic and scavengers activate their equipment around that health threshold. It gained +300% health regen, +50% max health and +20 armor points. You were being outscaled during the effects of the tonic.
Happened to my three man monsoon team, I had the highest damage output and when I died there was no chance to match the power of his tonic.

[RoaringTides]

You didn't hint at how to beat anything. The previous poster has just explained why I couldn't kill it, and I'm okay with that. I didn't have the dps to kill it before it activated the Tonic. You "hinted" at nothing. There is nothing on the level except for an environmental log. Since it's a new enemy and I haven't seen this variant, I thought it was a bug, that's why I posted it here. You just jumped on an opportunity to put someone else down and brag about how you beat it on monsoon.

[NuclearPoweredBadger]

No, bragging would be saying not only did I beat it on monsoon, but I didn't even get hit, because there's a way to completely cheese the boss and I don't want it fixed.

I gave you 2 hints in the first post.

[Jimmy Hunter]

He didn't softlock your run, you didn't have the strength to beat him.

Why is this in bug reports instead of asking for advice how to beat him?

[RoaringTides]

I didn't know he had the tonic, so I thought it was a bug with his HP or something because of how the regen looked on the UI. I wouldn't have posted it here if I had known.