Yeah, I remember back a year ago when he was unbeatable unless you were a guardian to force push him off the stairs. Sentinels had to Los him around the pillars and he did incredible damage. That got hot fixed and he's been a joke since.
The bug you are referring to is if you engage him within a split second after the fight starts. You can send your droid up to hit him and he'll likely die within one hit. Wait a second or 2 and he's at full hp. At least that's how I remember it being a year ago.
When I walked In the room before I even attacked it said level 0 505 health. I thought it might change when fight starts but nope.