You're trying to make the DRk sound more complex than it really is, and anyone who has played them will know its nonsense how simple it is.
Here's your average dungeon: Pull > blood price + unleash/abyssal drain spam and drop a salted earth > when out of mana use your one combo that you'll ever use to get some mana back and continue using AOE on repeat, hope you enjoy pressing a single button for most of the dungeon because that's what you're going to be doing > if 64+ in level throw in an ocasional quietus and continue the spam once that terrible complexity is over with.
That's it. That's literally all there is to it. The majority of that is spamming unleash/abyssal drain and using your one combo to get mana back so you can do it some more.
Here's your single target rotation if you're not absolute max level: Use your one combo path on repeat while dark artsing everything, ocasionally dark artsing carve and spit instead when it gets off the cooldown. Damn. So complex. Bloodspiller ocasionally if you're near max level and actually have it, which I can guarantee you the majority of the dungeons you'll do you won't. In the few instances you'll do an actual level 70 dungeon you will get it ever so slightly more interesting because you have TBN, not that that's some terrible complexity either. Just use it just before some damage is gonna hit you and use the blood you get from it for another bloodspiller. yay.
Dark Knight is dead-simple nowadays and doesn't require many buttons to be pressed at all, specifically in dungeons what the OP was asking. The majority of your time spend will be using your one AOE ability on repeat there. There's a reason why people are so easily able to reach optimal dps levels on Dark Knights, it's because you quite literally can't go wrong. You could smash your face on the keyboard and do well with them.