Okay, so this is getting irritating.
Early on in Fallout Shelter, I had the occasional incident from rushing, or just at random – and nine times out of ten I'd handle it without much of a problem. At that point in the game, I had probably half of my dwellers equipped with weapons, and most of them were somewhere just shy of level twenty.
NOW, with a vault at 200 dwellers, everyone equipped with a gun ( almost entirely sawed-off shotguns or better ), and a large number of level fifty dwellers – the incidents are becoming downright absurd.
I just watched five of six dwellers die, with a Mr. Handy assisting them, to an infestation of five roaches.
Now – this is all fine and dandy if you're constantly watching your vault and hitting people with stimpacks as they dwindle, but letting the game run at work and glancing down at my phone every few minutes, this can become a serious problem. One, single-room infestation, turns into five rooms with 90 roaches swarming everything that moves – all because I didn't catch it in time, and my armed, 5-stat, level 50 dwellers couldn't hang…
I'm getting a little frustrated having to revive tens of dwellers twice a day because I looked away too long. What's the deal Bethesda!? Shouldn't I have a LITTLE better chance than that!?
I mean, Deathclaws don't even inflict any casualties anymore, and they don't even clear my first floor – but roaches? A fire? Best break out the stimpacks! Molerats!? Don't get me started! Fifteen shots with the shotgun…
Best Answer
Try to avoid upgrading rooms. Incidents are much worse in fully upgraded rooms than a room with hasn't been upgraded. In particular training rooms don't benefit much from upgrades so I don't bother to upgrade those rooms. I also don't upgrade medical and science rooms, so I can rush them over and over as necessary to generate stimpacks/radaways or to get rushing or incident related objectives. Most of the time I leave these later rooms occupied by a single dweller, and that's enough to deal with any incidents.
The only rooms I do upgrade are the energy/water/food resource production rooms. For example I have fully upgraded a Nuka-Cola bottling plant next to the vault door, and the dwellers there are armed to the teeth. I also make sure that any production room that I have upgraded is fully staffed. I don't bother to try to respond to incidents by moving people around. It never works well. (Though early in the game I did move weapons around. One missile launcher can make a big difference.)
You should also consider your vault layout. Storage and residential rooms should be left unoccupied and placed so incidents in them can't spread to other rooms, or at the very least only to one fully occupied room.
I've also limited the population of my vault to about 110, as there doesn't seem to be much point in going beyond that. It's already pain to deal that many dwellers. I'm not sure if vault population factors into the severity of incidents, but that might be something to consider. I don't seem to have as much of a problem with incidents as you do even in my fully upgraded rooms, but that could be because my dwellers have better weapons than yours. I'm currently tossing away anything that doesn't do least 10 damage on average. At the very least reducing the population of your vault would let increase the damage of the weapons the remaining dwellers are equipped with.
Finally, I'd recommend just putting your phone in your pocket when you can't pay close enough attention to respond to incidents. Unless you're actively grinding certain objectives, you might as well just leave the game alone. You can't have any incidents while you're not playing the game.