Ahh yeah you should have to change your play style to adapt to an enemy. That is the whole point of making varied enemies, as it requires NEW approaches to overcoming the challenge they pose.

I have been playing the game on my android phone and the first game I played was a learning game, and in that game death claws gave me problems. After I learned the game I started fresh and used what i learned to create a better vault. aka I learned from MY mistakes.

1) Do not put elevators in the middle of your floors. put them at the side of each wall, there should be only one elevator that isn't on the side of your vault and that is the first elevator right beside the vault door. Once you get things up and running you will want to destroy the three rooms underneath the vault door and the elevator (second floor) and rebuilt those rooms with 3 rooms and an elevator on the far left side. This will mean the elevator on the first floor right after the vault door will go no where but you have an elevator from the first to second floors on the far right wall. Why go through all this trouble? elevators are immune to room events and so elevators will shield your vault from molerat attacks except on the bottom rooms. Second it allows you to set up your rooms in such a manner that you can deal with DCs. because you know how they will progress through your vault. (Molerats only attack rooms touching dirt if the side of your vault is only elevators then the only rooms that touch dirt are the bottom rooms. NOTE rachroaches and fires will still happen in any room)

2) You should have two rooms besides the vault door on the top floor one 2 size room and one 3 size room. Fill these with 4 and 6 dwellers along with 2 dwellers in the vault door. Your best weapons should be with these 12 dwellers. Then you should have two size 3 rooms and one size two room on the second floor. Fill these rooms with Dwellers with you next set of best weapons. This gauntlet of weapons fire should eliminate the DCs on the second floor with no casualties or limit to one death nothing to sweat over. It is more important to have the max number bodies in these rooms with decent weapons then having fewer high level dwellers. More dwellers equals more guns. I have one size two living quarters room just filled with default lvl 1 dwellers (new advlt holding room) with 6+ damage weapons in one room and they survive because DC leave a room before they kill everyone when first enter the vault. So they get off multiple hard hitting attacks and then are safe when the DC leave.

3) When you first start the game in about 30 mins you should have gotten 5 or 6 lunch boxes, if you don't get a legendary or high level rare dweller in those lunch boxes restart and try again. Then send this legendary/rare dweller out of the vault with a weapon and keep them out as long as you can to get credits and loot.

4) Work up to getting stimpacks and radaway. Once you get them recall your dweller in the wastes and stock them up with as many stims and radaway as you can. Then send them off again for as long as you can. The longer they are gone the better gear they will find.

5) Keep 3 or 4 weapons, decent but not the best, in reserve to respond to radroach or molerat attacks

There are other things you can do but these 5 tips help the most vs DC attacks. Point 5 is more so that your people are in the best shape to respond to any emergency. Having a event just before or after a DC attack can be problematic so create strategies the limit the type of attack each room is vulnerable to (point 1) and be able to respond quickly (point 5) so that you never get a devastating one, two punch. Even if you get a one two punch you will have prepared before hand so you will not be vulnerable to devastating results.

Points 3 and 4 help you get a flow of equipment coming into your vault with the min of disruption and the better chances of getting good loot.

I no longer find DC attacks all that big a deal because my infrastructure can handle the resource loss during the attack and the attack dies off on the second floor. Why? Because I CHANGED my play style to adapt to threats each of the enemies created. And I can play without the need to have a "rage quit" break between sessions.