Yes , that's a common use for 'em , they make good fire-screens too , being invulnerable to standard infantry small arms .
They can be quite good in assault , providing you charge . They are best led by a Dracon or Archon if you want to do this - the Lord does more damage than a Haemonculus , meaning that you are more likely to win and make the enemy fall back . You can also make a Sweeping Advance without fear of being cut down by Bolters , Lasguns , Shuriken Catapults , etc .