Goalie performance is pretty random, but it's not THAT random. There is persistence. I think you all are overstating how chaotic it can be. Cam Ward hasn't had a sv% below .915 the past 4 years, so he's a poor example imo for what you're talking about.
Quick has had a pretty great start to his career, this isn't just a Gigeure/Halak hot playoff goalie situation. This contract could easily become a mistake and I think the Kings D doesn't get enough credit for his performance this year, but I don't expect him to suddenly become a below average goaltender.
He hasn't, though. I mean, LA undercounts shots, but Quick has 1 top 10 save percentage season: this one. There really isn't much persistence.
Cam Ward's last 4 seasons - one is above average, the rest are average. That's the point. The Kings might expect Quick to be a .925 goalie going forward, but if he's a .915 goalie this deal doesn't look good at all. I think it's as good of a deal as they could hope to sign, but it's a giant risk.