1) Read the OP again: If you target yourself or a party member (e.g. not an enemy), Holy would be centered on you, the WHM. Meaning you could stand in the middle of the enemy pack while targeting your Tank and spam Holy identically to today. How is this a nerf? It can't be a nerf - 100% or otherwise - since this would retain the exact same functionality as it does today. Want to hit all the adds on Ex5? Target yourself or the Tanks or some other party member - something you might be doing anyway to Heal them. In what way is this a nerf? Again, you're some hotshot raider, aren't you? I'm a Timmy Casual and I can manage this. You aren't more inept at this game than I am. Again, without it, (2) is a no-go. I'd only support (2) if we got (1).
2) It technically wouldn't be 1112. If you look at my example rotation, you see you're often delaying some Glare or Holy as you move around Dia and Afflatus abilities in the rotation. Either way, it's something.
3) Maybe, but as I said, I was just trying to think of something that changed the AOE rotation from "Holy, Holy, Holy....Holy, Holy, Holy......Holy, Holy..." to something else, and as we have Misery right there on our ability list, we might as well use it. I don't really like your idea since it could easily overcap on Blood Lily (if one Dia detonates, it'd detonate them all), and it would make the optimal rotation impossible to determine. There'd be some weird expectation value calculation to determine how many Dia's are optimal to put into a pack given the 10% detonation rate, which would have to be prorated to not count the part of the Dia's expired on average before it goes off. Since it's only a 10% change, it's unclear what the optimal point would be to use Dia or not use Dia on the trash, and if you DIDN'T get a proc, then you'd be hobbling your DPS by casting all those Dias, while if you DID get a proc, then it completely shifts what you're doing as you have to decide how much longer everything will live and do the expectation value calculation again. Collectively...that's kind of insane. Even if Balance puts out a cheat sheet day three, it'll make the slow runs (if you get a WHM that doesn't look up guides) even SLOWER than they are now, like as not, which will probably not be better for the community overall.
There's a reason that RNG is bad and predictability is good sometimes. Especially for a white bread Healer.