For my build (Frozen orb) it is extreme pain so i was thinking how to deal with those and found out that the missile damp actualy makes them killable quite easy with this spell.
When you see elite with missile dump affix (Slow motion for all missile attacks) Just respec your primary skill to Shock Pulse Rune Living Lightning.
This rune makes your skill to summon electric spirit which runs EXTREMLY slowly due to missile dump aura and damages very fast as long as he is in contact with enemy.
They are disappear only after they walked their set distance so slowing them makes them last much longer. If you spam them and elite is not moving it will soon take quite big amount of damage and you will kill it easy.