You're right -- statistics really tell the tale of a team's success; that must be why the team with the best record at the end of each season wins the le.
Statistics are helpful to understanding what you see, but they don't tell the whole story because they are ridiculously imprecise. If you really want to base arguments on nothing other than statistics, I'd suggest that you dig around at places like 82games.com or popcornmachine to find numbers that truly explain something meaningful.
It is optimism if you're willing to point to the standings as proof of an argument without including in your analysis things that happen on the court and are obvious to most other observers. The Spurs, for most of the 1990's, were a team that looked dominant in the standings every year, but had no chance in playoff series against teams that could exploit their rather obvious weaknesses. This team, compared to the rest of the league, looks more like a mid-90's Spurs team than a 1999-2005 Spurs team. I think most people who watch them would tell you that, despite their record. I hope that changes.
In the first place, Dallas isn't a run-and-gun team like it was under Don Nelson. If you want to talk about statistics, according to John Hollinger's numbers, the Mavericks actually play at a slower pace, night-in and night-out, than the Spurs do. In fact, only the Blazers and the Pistons play at a slower pace than the Mavericks. So, in terms of style of play, the Mavericks are virtually identical to the Spurs in that respect. The Mavericks are far more efficient on the offensive end at that pace, but they don't play the same style as Phoenix. If you really think that, you haven't been watching much basketball of late. I generally despise the Mavericks, but right now, I have no doubt that they are the best team in basketball. They are far more like the 2004-05 Spurs than this group of Spurs is. They defend pretty well, they're efficient on the offensive end, they are witches in the 4th quarter, and they can win playing any style.
Even if the Mavericks played the up-and-down style that you suggest they do -- and they clearly don't -- the notion that "well that style hasn't won in a while and it won't win now" strikes me as outrageously simplistic. At some point, as the style of play around the league changes, someone who plays at a fast pace is likely going to win a le.