It's not like Dark Souls 1 where Backstab was the whole back along with the right half or the left, it actually specifically means to stand directly in the middle of the back and then strike. Also, parrying in general is hard, but if you cannot parry during the first level you're doing something wrong.
It's not the "sweet spot" because this works identically on varying weapons. What's actually happening is the riposte or backstab, which is generally 1 or 2 punches for minimal damage and then the crit hit, is logging as 1 hit of the weapon, and then the crit hit. So instead of a grab/punch for 15 damage before the crit, it's a bonus, free hit Bleed and poise are not exploits. Like it or not, they're intended mechanics of the game. Call me salty, but Dark Souls PVP is a lot more fun when people lay off exploiting glitches and just dual. When it becomes all about the backstab you lose 90% of the gameplay (not to mention limiting the range of viable weapons). MdK8u.