I copied Coriel over to the PTR this weekend and tried some heroics. Some thoughts:
1. I don't think the mana requirements are in at 80.
Now maybe the mana requirements drastically increase from 81-85, but at level 80 they're negligible. The only way to run dry would be to spam Divine Light (the big heal) or Flash of Light (now an expensive, fast heal).
2. Holy Shock and Word of Glory are the go-to heals.
They're fast, cheap and heal for a decent amount. I was using Holy Shock on cooldown, tossing WoG when I hit 3 Holy Power, and filling in with Holy Light on non-tanks and Divine Light on the tanks.
3. Beacon of Light is now dirt-cheap.
It's so cheap that Beacon is a no-brainer now. Just put Beacon on the tank and heal as if Beacon did not exist. It only transfers 50%. If you heal a non-tank, the tank gets a little heal as a side-effect. If you heal the tank, you get a boost of Holy Power.
4. Flash of Light is obsolete.
Holy Shock is instant, costs 25% of the mana, and heals for something like 66% of FoL. WoG heals for 66% and is free. Plus, after a HS, HL or DL are sped up, so they can land very quickly. And you can proc Daybreak to get double HS and then chain into Word of Glory for very quick heals. I'm not really sure I see what situation FoL would fit in now.
5. One-click buffing is awesome.
One button press, and everyone gets Kings. Heaven.
6. Light of Dawn is ... interesting.
I don't really know about this spell. The thing is that in the two heroics I ran, the only time everyone took damage was when the DPS pulled aggro. More often than not, they were running around like monkeys so it was really hard to get all of the them in the cone.
As well, it's a good heal, but it won't keep a group up when mobs are beating on them. It seems fine for splash damage, but not when people pull aggro. Plus it's on a fairly long cooldown, long enough that it often falls out of mind.
7. The Healing Mastery is okay.
The healing mastery puts a temporary shield on your heal target for 8 seconds. The shield is for about 8% of heals. It's okay, but the only problem is that the shield doesn't increase with subsequent heals unless it expires. This is especially problematic as Holy Shock tends to hit quickly after the last heal, before the shield can expire. So you often end up losing some of your mastery if you heal the same target twice in a row.
This could be a bug, so we'll see if Blizzard fixes it.
So is the new healing model better?
Well, it's certainly better than spamming Holy Light all the time. But I'm not sure about the actual triage involved. The thing is that you want to use HS all the time, because it's cheap, fast, heals for a decent amount, and is the primary generator of Holy Power, which gives you your Word of Glories. So really, I found I was following a strict priority of WoG-3, HS, then Holy Light. The only exception was if the tank dropped to 50-60%, at which point I used Divine Light to bring them back.
The problem I see with making mana more important is that if Holy Shock gets more expensive, then a paladin will be less likely to use it. But that will mean less Word of Glories, so you're kind of just left with Holy Light.
It could work, but it does feel as if HS and WoG are too tightly bound to really allow one to truly triage and conserve mana. But I don't know. I'd really have to try first-hand the later levels when mana restrictions actually kick in.