Some ppl underrate dirk cuz he's a shooting big man with less power moves. Just like most regular sg, he relies on shots & quick first step, so when heavily guarded, he can get inconsistent. That's what happened during the games he poorly performed and clearly it was the case versus warriors. But still it changes nothing about what he did as a leader of mavs. They made it to the finals in 06, and they almost made it to 70 wins this year. I am pretty sure, nobody was saying what they are saying about dirk back in Feb this year, when they were trying to reach Bull's 70 wins plateau. So whether or not, Dirk can take over last 5 minutes or not, he's the leader on a legit championship contending team. The fact still remains the same. They got the ingredients to go all the way. Just need to make it happen.
As you know, defense wins it all. That's been said and done in recent history of NBA playoffs. Sadly, Suns, Mavs kinds aren't the defense priorty teams, meaning they can be shut down on any given night if shooting doesn't fall. So it isn't really fair to lay all mistakes & faults on Dirk for not being able to beat warriors. It was just the warriors that played exceptionally well just against Dallas. I hardly doubt it will repeat next year.