So I do a lot of ground STF's. On my engineer I spend a fair amount of time wearing the Fabrication Specialist Kit (Quantum mortars and Phaser turrets). I decided to splurge and get a very rare Explosives Expert doff for the mortars, since three mortars are incredibly useful.
I just about never see 'em though. Hardly ever see the second phaser turret either from my rare doff for that purpose. In fact, over the last twenty or thirty STF's that Ive done neither has proc'd even once, that is easily over 100 uses.
Totally ridiculous, absurd, and stupid bad luck aside, I dont think this was designed particularly well. Especially since its all pure RNG. *Especially* with the Very Rares. I mean its a Very Rare doff, people pay millions for em (I paid 2.5 Million for mine). They should have an improved chance of working.
Such as? Well, for something like mortars/turrets/support drones make the second one a 100% chance. IE, you have a very rare explosives expert -> every single time you push the button to call in a mortar you get two, MINIMUM. And the third comes in on a 33 to 50% chance. Something along those lines.
Im really not much of a fan of Cryptic's corruption of the normal MMO mechanic of "put in time and effort for reward" into "put in a lot of time and effort and get a chance at a reward, maybe, if youre lucky."