I think the best approach to balancing the grenade spam “Immortal Gunner” build would be to either change Means of Destruction to only allow grenade regen proc chance on the initial tick of dot style grenades and similarly to change Vampyr to only allow health regen on the first tick of dot style grenades(or lower the amount of health recovered).
Or, alternatively, to take this line of thinking a step slightly further, it could be changed to where Means of Destruction can only regen grenades on splash damage done by guns(and Iron Bear).
The chance to regen a grenade could potentially be brought down to a lower percentage as well. With so much splash on top of splash to the splish splash, Moze is not lacking for opportunities to proc MoD.
Anyways, this would bring her into line without having to alter any items in the game.
I’m a Moze main myself and love her to death but in the interest of balance and build diversity I actually prefer the second option. Also if Means of Destruction was brought into line using the second option then Vampyr would likely not need to be touched.
She would still be ridiculously strong but would simply need to proc MoD via her guns(which, c’mon, that isn’t hard) and would prevent the mindless grenade spam without moving or aiming thus resulting in an engaging build that is still fun and powerful but you would now have to interact with the game to play (more than spamming one button lulz)