It seems like with roughly equivalent dwellers in my first two rooms, the smaller room takes less damage. It seems like they spend less time in smaller rooms?
It's hard to say for sure with deathclaws since it's not easily repeatable, but for other hazards (Fire, Radroaches, Molerats) the smaller and less upgraded a room is the easier the hazard is to solve. I've tested this fairly extensively while doing the "Rush X rooms successfully", "Put out X fires" and "Solve X Incidents" objectives.
I have noticed deathclaws stay in my 3 wide room longer then the 2 wide room after it, but have not done any testing on different upgrade levels (both were max upgraded before Deathclaws started attacking me.) however based on other hazard durations I'd say chances are good having a series of Unupgraded Level 1 rooms w/ two badasses in each would be your best bet in dealing with deathclaws.
Going off of what I have noticed, take this as an answer or not, but in my situation Deathclaws seem to do the same amount of damage to everyone in the room.
I say that because, when deathclaws attack, I just let them go through my base and see how many die and how many escape. Each room (1-3 room sizes with varying upgrades) generally has a full group, with a few rooms with less. So with all those variables, the deathclaws never kill anyone that starts off with full health (or i get lucky?) even when they have crap armor or no armor. They all go down to roughly 5-10% hp left, but they never die. The only exception to this is any room they have to go through twice, because they will do the same amount of damage to those dwellers again.
Also, the help tells you they only show up when you open the Vault door, so if you want to test this out, make sure everyone is at full health with no rad poisoning, summon the deathclaws, and as long as they don't travel to a room more than once, check how many die. If they do have a room they travel through twice, either move the dwellers out before they come back or move them before summoning the deathclaws.
Assuming the updates didn't change this, (2 updates have gone by) they seem to be used to cripple you more than kill you. The dangerous ones are mole rats, especially when they spread (just my opinion at least).