No offence but there is alot of people here who are not qualified to speak on who should and shouldn't receive PI.
PI should never be given out from a disc priest to a dps on fights like hungering destroyer, where having a full 20 man ramp for your shells is a huge deal, you are one of the few classes that can actually impact the miasmas.
Later on in the tier when you have better gear and progress, you also shouldn't need to give out pis, if you are playing in top 200 and its pre any sort of nerf you should absolutely give it away excluding very specific scenarios like mentioned earlier or sire p1.
The misinformation here reminds me of how people have tried to guilt trip me into giving it in my second guild awhile ago when re-progregging Hungering, and it is utter nonsense. Disc keeps it for themselves on Hungering, and Sire p1, and argueably can hold it for far more bosses this late into an expansion, if remembering that there is nuance to healing and sometimes it can be warranted if you are underhealing bosses or the other healers are not holding their own.