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.
29/5 Dylan Moran
3-6/6 Sweden Rock Festival
19-21/6 Graspop Metal Meeting
24/6 ZZ Top