Used it again a few times yesterday when we killed Sapphiron and Kel'Thuzad. While our Druid and Shaman healers are nicely equipped they still had to chug mana potions, use innervate and manatide whenever it was on cd, so I used my hymn too on cd, especially in the Kel'Thuzad fight.
My main problem right now is that I have to spare inner focus so I can get back to shadowform after using it. Should just be a discipline spell already.