I've just run some quick tests on all the bosses noted to have received stat changes this September 25th patch, namely, the bosses in The Shadowmoor, Dreamsong Theater, Brood Chamber, Warped Citadel, and Cathedra Cliffs. There appear to have been no significant changes to health, phase percentages, instant kills, nor notable individual attacks. Strangely, completed unrelated dungeons seemed to have received changes, solo dungeons once again allow the use of dragonblood and the thunder in Midnight Skypetal Plains return to killing all mobs surrounding Moonlight Monstrosities.
If this is unintended, I would suggest communicating more detailed notes of what was meant to have changed and if this is an error, otherwise I expect continued backlash in the coming week.
Edit: It seems one instant kill was reverted on DST boss 1? If you fail the CC after successfully executing the puddle mechanic you will no longer wipe, which is a step up.