I find the procs kick in a lot more when receiving cannon fire. If this is the case, I'd assume this is the reason; especially if the cannon fire is comming from turrets.
Damian has 3/4 Borg set and I have a setting that is 75 shields 75 engines for that time when I'm getting a little focus fire but I'm waiting on my evasive or deuterium cooldown.
Sometmes he's like frankendefiant for a minute or 2. And I will look some more tonight to see if I can count off the Borg procs. But it does make sense to get proc'd more by cannons, as I believe that mechanic would work both ways. Offensive for cits, and more "crits" on the recieving end of your Borg set
At normal shield settings like 69/40 FaW makes it proc like crazy. But if I am focused fire and go into defensive mode max in shields and 75/50 in engines my 4/4 borg set usually brings me back from the brink or holds me over until me HE or team mates get to me.