Hi Guys - has this happen to us as well.
Way to fix this issue is to just kill last Hypergate Irregularity.
It could be either BW fixed it so people don't skip the mechanic of the fight to beat the enrage or just a bug that makes the fight as it should be
Either way, last night on 8man HM we had one try when we left last Hypergate before Tantrum and just killed tentacle.
This caused boss health to go up to 32% and also 5 seconds into Tantrum Hypergate re-spawned and wiped us.
On second try we kill all Hypergates and boss health resets to 16% and we just nuke it as normal with no new surprises.