The one thing that TBN has going for it in dungeon pulls is the fact its up 10s faster than any other mitigation, so you get more uses depending on the timing of it as a whole. It's probably the only thing that makes DRK functional in dungeon content.

Something for the "just remove TBN cost and put to 25s and you fixed DRK" Xeno-parroting crowd should consider. And something the mathematicians should factor in, too; pulls aren't done when your first mitigation runs out.