6 deathstalkers and 1 nightfall is 12 damage per turn, unaffected by PC, which is pretty much like playing a dragon that can only be killed with purify.
And thats at a best case scenario.
You want realistic stuff? You have 6 deathstalkers, 3 nightfalls, 30 cards. You draw a deathstalker every 5 cards and a nightfall every 10 cards. So by the second turn, you can play two deathstalkers and 1 nightfall, which is 4 damage per turn. By the twelfth turn, the opponent has 60 health left, and you can play two more deathstalkers with your second nightfall, dealing 8 damage per turn. The opponent dies on turn 20th turn, well before you deck out.
My point? That PC alone doesn't shut this deck down, contrary to what you claim. Try it yourself, with this deck against a deck with 25 burning pillars and 6 deflagrations, or 25 earth pendulums and 6 pulverizers.