I haven't checked but I'm sure what you describe is the problem, i.e. the AI doesn't dodge soon enough. It also doesn't help that countermeasures only have a default effective radius of 300m (which I'm sure the AI account for), many Treb engagements are head-on, and with a velocity of 280 + targets forward velocity (plus possibly the launchers forward velocity?) there's less than a 1 sec window to pop a countermeasure. I know *I* always dodge Trebs rather than decoy them.
Anyway, probably can be done, since it's AI code probably not trivial unfortunately.
Fun fact, Trebs speed is 280, Harpoons are 250, so they're not really very-high-speed
