"I have never had any problems using a MAT pose in Studio." 

Nor have I - or seen the "20 nodes back" problem either but I won't dispute that such a thing may exist. I don't know how many people are actually optimizing materials for both DS and Poser - then you'd definitely need both formats. .ds just doesn't seem to be that popular yet beyond Daz own stuff.

"Democracy is a pathetic belief in the collective wisdom of individual ignorance." - H. L. Mencken