This is my first time posting, but I've been an avid reader of these forums for a long time. I recently specced holy/prot a few weeks ago after I got my 4pc. I used DiSac on Hodir a few weeks ago and it absored 171k dmg. Funny enough, according to the log, it lasted 13sec.
Now since I've respecced and started using it. I have yet to see it fall off early for large amounts of dmg, but for smaller amounts, it doesn't always last long. For example, I used it on Ignis and it only lasted 3sec. But that same night I used it on Auriaya and it lasted the full 10sec. The following day, Freya and thorim...10sec.
Back to the 3.2 topic. As it stands right now, I can pretty much holy light spam all day long. I rarely, if ever use pots or DP. I melee for wisdom procs when needed on fights that its safe to do so. We attempted IC HM steelbreaker and I was steelbreaker healer and was able to stay almost at full mana, just by staying in melee range with auto attack turned on and holy light spamming with breaks to cleanse fusion punch. I use DP only in times were there are breaks, I.E. Hodir frozen blows, mimiron phase changes or times with low inc dmg. With the changes to 3.2 I'm not to terribly worried. All it means is I'll actually have to use a pot for once and I'll have to control my DP use a little more. Add in the ability to still melee for wisdom, I'm not really worried. There are many fights where I choose to holy light spam, just because I can. The tank/raid isnt taking a ton of dmg and flash of light would be efficient enough. It just means I'll have to actually think about what to cast, rather then mindlessly casting HL. And being a pally in the Sunwell days, its nothing new. Also, I used the divinity glyph early on and switched to BoL glyph in Ulduar. I can't ever recall needing to LOH myself cause I was so low on mana. Its a very situational glyph and I find beacon glyph to be far better. With the changes to LOH anyway, I'd rather save it for a tank.