Has anyone found any vaults in New Vegas that are still isolated and still have vault dwellers in them? 
It would be interesting to go down into one, the few that I have been in are full of ghouls, raiders or convicts which is kinda disappointing. 

There were only a couple of Vaults created to do there job properly. The whole Vault system was a massive experiment by the Enclave, who never intended to save the entire population of America. Most of the 100 or so vaults were psychological experiments, such as a vault full of kids, or just one person and a hundred puppets. 

Technically the Vault from which the Boomers came was a relative success for the population, but definately not intact or isolated. (kind of like Vault city, which is most successfull but not isolated)
The only one with dudes still in yet isolated is Vault 0 (so far) and even that is kind of a failure.
It's their nature and what they are designed for. Successfull ones don't stay isolated.

" There were only a couple of Vaults created to do there job properly. The whole Vault system was a massive experiment by the Enclave, who never intended to save the entire population of America. Most of the 100 or so vaults were psychological experiments, such as a vault full of kids, or just one person and a hundred puppets.  "