The upcoming dungeons are estimated to be, in a nutshell, "really hard". I also confirmed the dungeon boss's difficulty with the dev team.

If you ever hope to defeat The Dzemael Darkhold dungeon boss, you will need to clearly assign roles amongst your specialized party of 8 rank 50 players. Furthermore, you can't just think of the boss as just a strong version of an ordinary monster. You will need to use special, boss-specific strategies to achieve victory.

I haven't played it myself yet, but I am looking forward to it
Sounds like it could be that we'll have to perform incapacitations in order to kill him. This would tie each party member to a specific role (attack right, left, etc.) and also require a "specialized party" (to target specific areas). I hope there's more to it, though.