Huh. I've always brought Wyll to that fight ever since the first time I did it (and discovered how good Eldritch Blast is for taking out the turrets), and trying to snipe the turrets from outside of the room has always automatically aggroed the people inside for me, even if I do it while sneaking with invisibility. Evidently I need to git gud.
Tactician/honor mode at least fixes the grenade launchers assisting you by making the grenades impossible to pick up. On balanced/easy, I think making them explode in your inventory unless they're thrown that turn, instead of letting one character pick all of them up and use or save them at their leisure, would be enough of a nerf to force you to still have to think about how you're handling them.
