I don't think playing "hits" are the issue. They're not suggesting they're just going to play hits sets. In fact, I suspect they won't. They're just saying they'll be sticking to the same set for a tour.
Also, having seen Mangini play, I honestly have no desire to see Portnoy back. Mangini was awesome.
1/12 Judas Priest
3/12 Deep Purple
5/12 Dan Patlansky
11/12 Dead Daisies