stone said: I've never been able to get those off...
Personally I would leave for the plumber...
I've climbed under the house to cut the copper line behind the spigot, and then used a compression fitting to replace faucet, but that was for damaged hose bibb.
That dremel tool? I don't understand the plan.
I think the most I would do is cut loose the hose... far enough out where it could be spliced... or just leave well enough alone.
If you have already been "had" don't call the plumber yet.
I had bought myself one of these as a housewarming gift. We moved in in July and it worked great until I went to take it in for the end of the season.(In Kansas City every house owner is either told or they learn the hard way that you don't leave a hose hooked up over the winter.( you may think all of the water is drained out but having that hose hooked up when it gets down in the single digits is asking for trouble)It would not come loose I had two pair of channel lock plyers exerting way more force on the hose bib than it should have to take. Well that is where some people would call a plumber, take it from a heavy equipment mechanic I can tell when something is a lost cause. There is no way that the hose will ever be unthreaded from the hose bib(the two have been electrically welded together) If you have one of the homeowners most handy tools all may not be lost.
I cut a slit through the fitting across the threads with a cutting wheel on a Dremmel. Be careful not to cut the threads of your hose bib, it wont make a lot of difference if you knick a thread or two but if you do be sure to use Teflon tape to seal the threads next time. To my surprise it didn't free things up even when I had an one eighth " slit all the way through. I had to cut two slits 180 degrees apart and then the two pieces could be pride off (like I said it was welded on there)I imagine that if you already have the hose that you can still use it but I would either wrap the threads with Teflon tape or put a good coat of anti seize on the threads. I am sorry for running on but we are 3 weeks into the Corona Virus mandatory Quarantine and I literally haven't spoken to another human being.
Good luck everyone