Dragon Slash ability to one shot bosses/npcs that are tied to phases in order to progress is bugged as hell.
This behavior is noticed, at least by me, in story mode instances.
So far I was able to bug at least 4 story mode fights (no progression possible) due to DS one shooting bosses/mobs
Instance - The world summit - One shooting the dragon when it's exposed may lead to bug (happened only once and was the first so I didn't care that much)
Instance - The mistery cave - One shooting the dragon while it's exposed, will lead to the flame smotherers beeing unkilable and the dragon to stuck in invun mode, no progression possible.
Not even needs to one shoot taking the boss health to less then 20% in one shot will bug it.
Instance - The Aetherblade retreat - Either one shooting Mai Trin or first mate (wich seem to be linked to 3 phases) will lead to the other bug in invuln state or in bombardment mode. No progression possible.
Instance - Earths and Minds - Last fight with Mord, one shooting any of the bligthed NPC will lead to Braham to get stuck on rift opening and Mord in invuln state. No progression possible.
In short DS is so powerfull that breaks the game, nerf core engi please.