For starters, debuffs like Reprisal would be considered part of raidwide mitigation... but as we've seen with Reprisal, many bosses are untargettable (or otherwise immune) for their biggest hits, making raidwide buffs more reliable in a choice between the two.
Fair.
Blind could be extremely useful for dungeon encounters, but bear in mind that as with Holy stuns, crowd controlling effects are subject to diminishing returns, particularly if they have a relatively low initial duration to compound this more quickly... and conversely, that our barrier is presently a net negative if enemies can't break it because they couldn't land a hit on us.
I figure it could be added to Salt and darkness as more of a sometimes buffer, something that would give us a bit of breathing room while giving us a reward for using it properly while not using it too often.

Overall DRK reducing an opponents effectiveness themselves is something i'd like to see returned, the how of course is the issue.