There is a guide for dealing with them in the community page, which is where I posted my method (above). This works, but try out different combos til you find what works best for you. Rotsa Ruck, Ranger...

VERY effective SOP in Fear 1 & 2 ...
Step 1: Select your shotgun of choice. (Pump or Auto.)
Step 2: TURN ON YOUR LIGHT. (Makes the shimmer effect more visible, PLUS they see you anyway.)
Step 3: Poise your finger over your Slo-Mo Button.
Step 4: WAIT FOR IT...
Step 5: When approached by the shimmer effect, tap Slo_mo.
Step 6: Target the shimmer, high center.
Step 7: Fire on target, repeat until target neutralized.
Step 8: Back out of Slo-mo and reload. (Unless another target is viable.)
Step 9: Repeat Steps 5 thru 8 as necessary.
I was glad to see these guys again in Fear 2, although the largest group I ever saw in Fear 1 & exp. was 3, and they attacked as individuals. Still, this method works beautifully

2 Assassins, time to shotgun up. Save the laser for hard targets.