I, as a mostly hell geared Barb have: almost 48k HP, 70%+ reduction from armor, and 100+ in almost all resistances (and btw, i don't know where you've taken that "25% cap" from, 'cause i have at least over 30% reduction, with the resistance shout i reached 50% fire reduction at some point.) and with my current build i have a little less than 12K Dps.
When i stepped in inferno yesterday night with my buddy (we're a two man team, Barb and DH) everything hittted us like a truck.
My DH friend was almost 2shotted by zombies, and of course we had to run and restart the game a couple of times because of some nearly impossible blues/yellows. I have to say, I thought i was prepared for this, but things hit so hard in inferno, that i tought i had to reroll to a wizard, or something to try to progress, or to at least be able to farm some gear for my barb.
But then i saw that solo butcher kill from a barb. With 5/5 nephalem valor. Damn. if he can do it, so can I. Don't throw in the towel, try to come up with a different build, browse the ah for some affordable inferno gear (you can find decent "starter" pieces for as low as 200K gold, wich is by no means much if you can farm hell).
The point is, that is in no way impossible. I managed to solo a couple rares as a Barbarian, with limited kiting, and without hitting the enrage.
It balls hard, but not impossible.