In VSH and FF2, the razorback was a great tool, but honestly (coming from a guy who never used it) there are better options. For one, the stock smg is great, and has small knock back so if the boss is coming for you, you just have enough knock back that if you hit at least 15/25 shots, he will stay the same distance. And the sniper is fine close-quarters, Melee usually knocks the boss back pretty far, and the sniper does quite a bit of knock back even without scoping. If you were going to fix the razor back, I would do this:
Keep the regeneration of it
when hit, take massive knock back (like flare jump knock back) but loose 50% hp.
I think this would make it fair, so that the snipers don't pick horrible spots, and get a free pass, but actually need to think of a good spot, so they don't loose half their health, and potentially dying from fall damage.