It's pretty good, yes, and you'd be a fool to say that it doesn't tell you anything important about goaltenders. And yes, it even tells you something important when taken out of context (which GAA and wins don't really do). But there is no way that recorded save % says as much about individual performance as goals, assists, or points do for forwards.
For sure, but I'm saying it's the best we have for goalies.
Since 1984 when sv% was first officially recorded (using players who played 45+ games):
-17 of the 26 Vezina winners have had the best sv% in the league
-21 of the 26 have been top-5 in sv%
-Of the 5 goalies who weren't top-5, 4 of them led the league in wins, and 1 was second
Being that Vanbiesbrouck was 6th in his Vezina year, the only true outliers are Brodeur in 04 and 03, Carey in 96, and Fuhr in 88, who all finished between 12th and 15th in sv%. In each of these cases, these guys had very impressive showings in other stat categories. Brodeur led the league in wins both years, had a GAA right at 2, and played his usual impressive 70+ games, and led the league in shutouts both years. Carey was second in wins (to the goalie playing on a 131 point team), but led the league in shutouts by a mile in a pretty terrible year for goaltending (and was the first goalie since Dryden to approach 10 SO's in a season). Fuhr set an NHL record for games played in 1988, and won 40 games and led the league in shutouts.
I guess my point is, no goalie has ever won the Vezina with mediocre statistics across the board, and I don't think that's coincidence. On the rare occasion that a Vezina winner isn't among the elite in sv%, he's had a dominant season in terms of win/GP/shutouts.
So either:
A) statistics (most notably sv%) are a decent reflection of a goalie's play, and they reflect Vezina voting accordingly
or
B) they aren't a good reflection but the voters put a lot of weight on them anyways, and the Vezina voting reflects them accordingly
Either way, there's no way to improve the system short of watching every single NHL game