It was nice to read this experience. Yes, definitely for a more "deep" experience of Pohorje, three days are more suitable than two. I crossed Pohorje a good month ago. First day from Maribor to Pesek, second day from Pesek to Slovenj Gradec. The path is more or less well marked, but still it was a bit unclear for me here and there too. I had the booklet of the Slovenian mountain path (last edition 2018) with me and here and there there was some discrepancy. An example was in the area of Klopni vrh. In the book it says that you simply climb to Klopni vrh and don't go past the hut at all. But I followed markings "1" and came directly to the hut. There I could treat myself to a cold drink and the friendly hostess/owner explained everything to me where to go. By the way, along the path there were quite a few signs saying direction to Koča na Klopnem vrhu next to the note "closed". From the hut I then returned good 5 minutes back and caught the path to Klopni vrh. When I descended from Klopni vrh to the road in the other direction (wasn't sure it's the same road as before), there was a sign "Pesek" pointing right, at the same time left down the road marking with label "1". I checked in the booklet and there it says after Klopni vrh turn right onto the road. Only when at home I looked at the GPS track on the map and read an older guide did it become clear to me where the confusion comes from. Sometimes SSP led to the hut, not to the peak. Now the reverse. Markings are obviously new and old, hence the confusion.
Maybe some additional marking would come in handy between Grmovškov dom and Koča na Kremžarjevem vrhu.
As for times, as bbugari1 already wrote, sometimes even the signs themselves don't match best. I walked faster anyway and shortened most times. But there was also some time realistic for faster walking (e.g. 2 hours from Klopni vrh to Pesek). Also the section past Šumik as I remember wasn't too generous with time on signs.
And along the path I came across closed Ribniška Koča (in the outer box only two more pictorial stamps, no oval for transversal).
Otherwise really a path worth visiting!