I don't know that it would be useless, but in my opinion, penetration is essential on large dangerous animals and hard cast is the way to go with any pistol round vs a pissed off bear. One of my bosses peeled a grizzly off of his chest with a S&W in .44 Mag and even he doesn't think much of pistols for bear defense.
In my very limited experience with charges, nothing is guaranteed. I have seen some massive brown bears get into trouble and have been sent after a couple that were threatening people who usually did something stupid to get everyone into trouble. One brown bear charged at a group of about ten children near the Russian River who were on a fieldtrip. They were innocent enough and reading nature trail signs on a footbridge when a grizzly climbed out of the river and accidentally got itself funneled one the footbridge and in between the railings. The kids freaked and ran, scattering into the woods. Of course, the bear who was just there for salmon, chased some of the kids since food runs. I was the closest person with a shotgun when the teachers ran to get help.
So the kids were running, the bear was running after them, and I was running after the bear. Fortunately for all of us, the bear decided to go back to fishing in the middle of the ordeal, and the kids and I all slinked away without firing any shots. But if I had, it would have been bad no matter what happened and the faster the rounds disabled the bear, the better.
One of our biologists got a heart shot on a bear that ran for another 200 meters. After my few experiences with dangerous bears, I am convinced that there is very little likelihood of not getting ripped to shreds no matter how it goes down if in the open. Hunting anecdotes are useful for hunting and if starting the fight, but a bear that starts the fight is way ahead of anyone reacting to it, and shots won't likely have the same effects if their adrenaline are instincts are pumping before ours. As our director who fought off the brown bear with his .44 Mag said, "better file the front sight down," as any handgun is likely to get shoved up one's ass before the fight it over.
I have only been charged once and that was by a black bear, which was more than terrifying enough for my taste. In that case, I did not have a firearm on me, but vividly recall wishing I had a 870 with slugs. The encounter lasted for several minutes, with her backing me and another guy up a ridge line, drooling and growling at us while her cubs screamed from treetops from down the ridge where her charge started. I am very glad that no one died and that the cubs got to keep their mom that day. However, if today she charged from 80 meters out again, was standing in front of me right now on her hind legs with drool and foam flying off of her teeth, twisting her head back and forth in a rage, and then pushing me 1,000 feet back up a narrow ridge with no escape and the strong mountain winds blowing in my face making spray worthless, I would wish for a few 12 gauge slugs. If I was too lazy to carry that, I will be carrying 15 rounds of 220 gr. hard cast in a pistol that I can make as many good hits as possible with in the time I may or may not have. The XTP is to get me to the field, or to reload in a gunfight with human predators. Otherwise, I will be as careful and respectful as I can, default to bear spray, and as a last resort poke as many deep holes as I can before I get eaten alive by a black bear or beaten to death by a brown one.
Now watch some fools talk about 'penetration", when the 9mm penetrates skulls just fine.
