Honestly, I use Dark Command a LOT as it has a real quick cooldown for a taunt.
The most success I've had on single targets is icy touch spam, converting my blood runes and using them for icy touch. This leaves me with extra unholy rules I can't use for anything besides plague strike, but it seems to generate much more solid threat. When I'm doing Oblit/HB I seem to get bosses pulled off me a lot more.
My "oh shit" pull preferences are.....
1) Dark Command - it works and uses no runes.... happiness
2) Deathgrip - it works better on casters and again, uses no runes
3a) Icy Touch - doesn't pull THAT hard, but works. usually have to pop more than 1
3b) Blood Boil plus Diseases.... if more than one mob to grab.
4) Empower Rune Weapon + DnD -- becomes number one option if more than 2 mobs are running
Kind of option of last resort, because after this.... I'm wiped on runes
No one tanks in a void.........