In my experience using JE Sawyer mod and very hard hardcoe (and free hand shooting - no VATS) you need something that fires fast and powerful enough to punch through the 15DR.
Melee can work if it is started from stealth but that is more a function of stealth being overpowered. With stealth I can clear the deathclaw cave with a chainsaw and never take any damage. The issue is the damage that they put out, even with Remnant power armor, helmet, implant and two toughness perks for 50+ DT they still kill me in one attack sequence. With purifier perk for the extra 50% damage boost I can kill one deathclaw in VATS with melee or unarmed if my attack gets off first, or at least most times. It is too dangerous to use melee as an effective tool unless you are jacked up on med x, slasher and especially turbo.
Once a deathclaw gets close here is what I like to use:
Guns courier - If have shotgun surgeon for the -10DT use the riot shotgun with handloaded buck, And Stay back perk helps as well. Otherwise I like something big and full auto - the Automatic rifle with handloaded or AP ammo, CZ Avenger minigun with handloaded or AP ammo, even the Light Machine Gun and the Bozar can work with AP ammo.
Energy courier - Tri-laser, Elijiah's LAER, Plasma Defender, and Plasma Caster can all put out enough damage fast enough while using optimized ammo. With max charge ammo the Gatling lasers can also do the job.
My last bit of advice is to make sure your weapon of choice has enough ammo capacity to do the job, you do not want to be fumbling for a reload when a wounded deathclaw is in your face.