I enjoy soloing old content and recently as I was attempting old bosses which I wasn't able to solo before at 85, I discover that demonic gateway can largely contribute to my survival. By entering the gate and get teleported, the boss immediately loses aggro on me and switch to 1 of the wild imps, thereby enabling me to significantly reduce the damage taken on me. I run with dual demonology spec, one for DPS and one for tank.
Depending on the fight, Tank spec will be my staple unless burn tactic is more beneficial then I will be using DPS spec and let my pet tank.
Also I am curious to know, within that 1 sec+ teleportation duration, are we susceptible to damage? Say if we were to teleport right through the (Flanking orders - row of mogu warriors) from the Spirit Kings.