If you have "...no more buttons to mash to keep enough meaningful mitigation up." you might be doing something very wrong. Dungeon speed-runners average about 33-40s per pull and that's not including the 13-15s to gather up the next wall-to-wall pull. Your average Duty Finder group does about 40-55s per pull. You'll have at the most three uses of TBN per pull. This also gives you about one Abyssal Drain use per pull as well and you obviously want to save it for when you need it each pull and not spend it immediately (you don't understand how many times I've seen this). The rest of your mitigation tools should be spread out accordingly.