Pulse Grenades only do 10 damage plus the EMP effect. You would be hard-pressed to find a way to code it into general combat AI for the enemy to use such a weapon in a non-scripted fashion since melee weapons and even fists do more DPS
I never looked, but do NPC's use Pulse grenades against robots?
(I should also wonder if the AI takes energy resistance into account and avoids energy weapons for attacking that target)