Never. Even the worst shield even for an AI is better than shield shunt. You can use it to flicker to catch a reaper or hellbore shell. AI will do that too. It should be free or even gain OP of removing shield, that 15% armor is not worth it and to make the mod worth it need to build it in and even with it built in my dominators do better with a shield, a dominator with trash shield that overfluxes itself quickly from gunfire is still better with a shield. Sure, you can put strong PD with PD skills maybe and PD hull mod but then you already paid OP to put on the shunt, not to mention the story point waste and S-mod slot waste, not to mention it will do nothing against plasma, hephaestus or hellbores flying your way. There's a reason Vanguard being so overhype when added to the game is trash, bcs it has no shield so you just shoot it for 5 seconds with hephaestus and it explodes, same gonna happen to any ship you put shield shunt on.
Is it good for player? debatable, I rather not pay anything to gimp my ship and catch missiles and anti armor projectiles with it, literally free defense, if you are reaching 100% flux anyway then you took more than you could bite at the same time and/or you have unoptimized loadout with flux hungry guns and not enough venting, shunt won't fix that, just turn off the shields and keep firing on 99% while backing off to vent and maybe catching a reaper with a flicker. For AI?, only to fix their behavior bcs they will catch even anti-shield projectiles on their shields while having bad shield, that's literally the only reason to ever use shield shunt and even then my builds still fared much much better with a crappy shield. It still comes down to the optimization, if the build is bad you will overflux even with shunt, it gives nothing to venting speed and your firing speed will grind to a halt at 99% flux.
Also, forgot to mention, your weapons will be perma disabled without a shield, enjoy a overload free life where you can't shoot anyway bcs damage and emp will disable everything. Shunt is only good to bully smaller than you ships but take on anything capable of equiping a heavy mauler, hephaestus, plasma or worst of them all, hellbore and tachyon then you are firing nothing and you will melt as they turn your armor black in first volley from max range before you even approched them. I don't put shunt even on mora simply bcs they eat more damage while having it and I don't have to pay any s-mod or story point or most importantly OP for it and even on things like dominator and onslaught you have to fix so many problems to minimize shunt drawbacks while you can have no shunt for free, keep the shield for flickers and eating infinite damage and spend all that OP for actually usefull stuff. Unless you are a Luddic and you want suicide run down the enemy, then you lose most of your fleet but win or you didn't bring enough and all explode bcs you can't push thro.
