The doomguard has an ability "Cripple", which currently works on any raidbosses.
Cripple
30 yd range
Instant 30 sec cooldown
Cripples the target, reducing movement speed by 40%, increasing time between melee and ranged attacks by 45%. Lasts 20 sec.
It's on 30 sec cooldown with an uptime of 20, which means it will only fade for 10 seconds.
If you have 3-4 warlock with completed quest chain for Ritual of Doom, then you can always keep him up in the raid. (He is on 15 min enslave now and it can't break)