Hmm, 2b reminds me of a holy priest talent called Rhapsody
Note that Holy Nova's starting power is pretty dog compared to HP's other healing skills, so we will have to make an adjustment, such as:
'Each time you cast Glare or Dia, your next Holy is increased by 40 potency. This stacks up to 5 times.' This would, at max empowerment, make Holy a more conservative 350 compared to Glare's 310. It'd also incentivize 'use your DOT on stuff while the tank's running to the next pack' as you'd be powering up that first Holy. After that though, spamming Holy is still the better damage option, 'single targetting in AOE' would not be optimal.
edit: alternatively, 'Each time your Dia deals damage, your next Holy is increased by X potency, this stacks up to Y times', if they want to tie it to the DOT. They don't exactly have a track record of incentivizing DOTs in recent years though, so it's more likely the former that would be their choice
As for 3, I like the general idea, it again reminds me of Holy Word resets. A gameplay loop of '3 Glares = Holy, 3 Holy's = Misery' doesn't sound bad. But the problem is you'd be using a Misery every X GCDs (if half-misery charges are possible, it'd be every 24, which conveniently is every 1 min, but using lilies to heal would throw it off and people wouldn't like that), plus the extra potency from the Holy. If we had other skills, we could build a more fitting rotation from them (basically replace the payoff with something else instead of Misery) but alas
Edit edit: 'Each time you cast Glare, Dia, or Holy, you gain a stack of 'Nature's Wrath'. At X (let's say 10) stacks, Holy transforms into Afflatus: Purgation.'
Afflatus Purgation:
Instant cast, no MP cost, GCD, lower animation lock than the PVP version since it's not an LB here
Line AOE, same length/width as PVP version
Deals damage in a line in front of you with a potency of 600, and 50% less to all secondary enemies
Numbers adjust as needed, it should feel cool to use without feeling like 'I need to puposely overcap to make sure this lands in raidbuffs'