Pretty sure the heirloom items are counted as ilvl 1 for the gear check system. When my DK hit 80 I couldn't queue for PoS or ToC, but after replacing the heirloom shoulders and chest with ilvl 200 blues it let me queue for ToC. After replacing most of my ilvl <200 blues/greens with ilvl 200 blues/epics from normal heroics and getting the axe from Loken, I was able to queue for PoS.