Miller was the head of MLB union in the late 60s, 70s, and early 80s. He led the union to strike 3 times. He was instrumental in creating the psydo-free market free agency system in baseball where you have ARod making $30 million a year, the Pirates' entire payroll being around $30 million a year, players signing 10 year, $150 million contracts late in their career and teams having to carry their dead weight for 5 years of it because the contract guaranteed, the creation of arbitration, etc.
I was also being sarcastic that it is good new. The overwhelming majority of people feels that Miller really hurt baseball with what he was able to win for the players. It helped to turn MLB to the clear cut #1 sport in this country to a distant #2 and in some areas #3 or #4.
I don't know if all pro player people would be happy with his involvement. Yes, he was able to bring a lot of the player friendly free market perks into free agency (no ceiling on salaries, not salary cap, guaranteed contracts) without their downfalls (there are still salary minimums that the league must abide by). But he did help to turn the league into a very regionalized sport where every year it seems people are growing less interested in it (attendance and ratings are down everywhere where football ratings are increasing) and only in certain towns it is still very popular. Some of the things invloved in the NFL's free agency system may not be on their face pro player, but they are pro-growth in the NFL's popularity who ultimately rewards players. Miller's MLB rewards the players no matter what it does to the game which ultimately, hurts the players because lower attendance and ratings means that players get less money than they could.
I think you're saddling Miller with a lot of MLB's problems that have only tangential relation to labor/management issues.
First of all, let's recognize what baseball was like before Miller. If you want to talk regionalized, how about the fact that from 1936-1956, half of the World Series were Subway Series, and that only stopped when the Dodgers and Giants left town. From 1936-1964, the Yankees participated in all but 7 World Series. All but 9 were won by either the Yankees, Dodgers or Giants.
This is inarguably the most inequitable stretch in MLB history, and Miller didn't take the reigns of the union until two years later. So clearly, nothing he did can be blamed for things that had been true about baseball for decades -- that the same few teams, usually representing the biggest markets, do almost all of the winning.
Baseball's enduring inequity owes little to anything having to do with the union, as opposed to things involving just ownership, such as revenue sharing and rights management, particularly for TV broadcasts. The lack of any sort of revenue sharing gives the Yankees and Red Sox little reason to care about the national popularity of baseball. They've never been more popular or more profitable, so what's it to them?
The lack of shared rights management is an even bigger problem, in that it's largely what perpetuates the huge inequality between small and large market teams. Selling the TV rights as a package not only means that the small-market franchises get a larger share than they otherwise would, it's also a means with which the NFL gets the networks to televise all of the games, period, and gives the league the leverage to get national exposure for teams whose market-size wouldn't warrant it.
Meanwhile, in baseball, you've got a handful of teams with their own house cable networks, and a bunch of others begging local affiliates or the regional FOX sports division to bother to broadcast them. This just compounds the inequity, as not only can a player get more money from a big market team, but it's also the only way to increase his exposure. In the NFL, however, the two biggest single-player brands in recent memory -- Manning + Favre -- didn't need to leave Indianapolis and Green Bay to build their national profiles.
In other words, the NFL is a national sport because the rights to its properties are managed and sold nationally, and baseball remains regional because its rights are managed and sold regionally.
What's more, the different league structures make it impossible for baseball to try to emulate the NFL's salary cap system, because without a big move towards revenue sharing, half of the teams couldn't survive the establishment of any kind of salary floor. In baseball, the owners of teams like the Marlins, A's, Royals, Twins, etc. can make their profits by keeping expenditure down as much as possible. They couldn't afford a salary floor without serious subsidization for a while.