A. The section you are attacking will kill or completely cripple the mech when destroyed.
AND
B. The section you are attacking contains enough equipment to make a large difference if they are destroyed a few seconds quicker.
If you don't have A, then you are wasting damage stripping the armor off a section that won't end the enemy as a threat. You'll just have to strip off the armor off another section to actually kill them off. During that time they will be attacking you with real weapons.
If you don't have B, then there's no point in the crit seekers in the first place. Just use actual weapons to burn through the armor and destroy the whole section much more quickly.
Edited by 7c Nickel, 07 March 2013 - 09:56 AM.