Intelligence Agent would not have any effect on follow on attacks from the rest of the fleet.
ummm, if they discard a defense token they can no longer spend it so... intel officer in fact has great benefit to the rest of your fleet.
OK, slight correction: Intelligence Agent would have **** litte effect on follow on attacks from the rest of the fleet.
Basically, you have to be in a position to force the opponent to spend the targeted token anyway, despite the fact he will get plenty of opportunity to use it on the rest of your fleet's attacks.