Iran's deafening silence over plight of PK Shias

Given the continuing massacres of Shias in northern Pakistan, in Balochistan and, most signficantly, in Parachinar in FATA, how do we explain the silence of the Iranian regime and its failure to offer even words of support to its co-religionists?
Alex Vatanka, a scholar at the Middle East Institute, has a good go at explaining the relationship in an interesting article in the latest edition of Trends in Islamist Ideology, Vol 13.
His article The Guardian of Pakistan's Shia notes that Teheran's actions have rarely matched its rhetoric about the plight of Shias in Pakistan. "Indeed, among the ranks of Pakistan’s Shia activists, many today are disappointed by what they perceive as the lack of Iranian pressure on Islamabad to take measures to protect the Shia of Parachinar and to crackdown on sectarian groups and ideologies.  In Iran as well, there are analysts and even senior Shia clergy who have condemned what they deem to be Teheran’s weak stance toward anti-Shia violence in Pakistan."
Vatanka thinks Iran's stance could change in the near future. He notes: "Iran’s outreach to the Shia of Pakistan has historically fluctuated as a function of sectarian relations inside Pakistan and of Tehran’s overall relations with Islamabad. When sectarian tensions rise in Pakistan and Tehran-Islamabad relations are poor, Iran’s support for the Pakistani Shia has historically been at its strongest. In the early 1980s to the mid-1990s, for example, when sectarian tensions and violence expanded in Pakistan, the Iranian regime became a strident supporter of the Shia and of militant Shiism. Now, given the deteriorating state of Shia-Sunni relations in Pakistan, and also given the fact that Iran’s clerical establishment is under attack by “Shiite nationalists” at home, conditions may be ripe for Iran to take renewed interest in the plight of Pakistan’s Shia once again."