Your reaction if SE adds in a Passive Ability to Mobs...

[JunseiKei]

The majority of the replies in this thread are about a desire to keep the dungeons as braindead easy as they are now, rather than trying to shake up the formula. Not hard to see.

Actually, I think there needs to be a clarification added to this idea. One that popped up in my mind thanks to your statement.

I don't mind dungeons that will appear in roulette being braindead [read: mostly devoid of mobs having abilities for the sake of making large pulls increasingly difficult] for the sake of efficiency. I would want to see more mob mechanics in places of Palace of the Dead, which is a dungeon and does shake up the formula with what it has to offer. I wouldn't mind see such mechanics in places like the Diadem. Basically, for dungeons that will be used to farm large amounts of tomestones, for items like relic and their quests, I see no reason to make it increasingly frustrating.