Well you do have the power armour, which helps a tiny bit I suppose. In the video I've seen the guy basically makes sure he's hidden, then uses VATS and blitz to go and get 4 or 5 good hits on the deathclaw, and then just runs off and hides until he's hidden again and then repeats. On his second run (dies just before he kills it on the first), the manages to kill it with a pool cue as apaprently they have about 3m of range! That combined with sneak sorts them out.
I guess, therefore, that you just have to put loads of effort into having the best armour you can get!
I think perhaps they're doing it without guns, instead of melee only, so it's possible to use grenades and other explosives, so you can probably take those guys out from a distance.
Or it could just be a bit of compromise to get through that first mission, then choose your own way afterwards!