Its a ranged parry yes… the only way to back stab is a charged R2 that staggers them and then you do the back stab. The front back stab comes from the Gun to the face interrupt stagger and then riposte
There are more ways to get Blood rocks "+10 weapons upgrade"
There are 2 in the main game and 1 or 2 in the DLC… you can also buy a Blood Rock with 60 Insight ( a secondary form of currency)
I disagree about the gun stat that @TempusChaoti mentioned… the gun parrys come in very handy and the lower your stat the less likely you get a parry on larger enemies…the larger enemies are the ones you need to parry not only to destroy them to progress but to also farm large chunks of "souls"
There are runes you can equip that give you 30% more souls buy way of parry kills. this can net you up to 15,000 souls in one kill. Very helpful for leveling up, buying fire paper, or bullets and blood vials.
To me the weakest stat is Dexterity… I ran 40 strength, 40 health, 40 bloodtinge and 30 arcane and 15 dex or 20…i cant remember.
But I do like the run off the cliff when invaded idea… brilliant lol