It's rather hard to measure exactly how much healing something will provide, unless it's a flat % increase.
Holy's 2pc is already looking great. 5 more bounces on PoM will make Divine Insight essentially let you chainheal the entire raid. But its 4pc is outstanding. Tons of free Serendipity stacks is easily going to be a huge boost to throughput; only helping the 2pc even more by letting you do CoP -> DI for tons of PoM bouncing.
Disc's 2pc...ehh, it's okay. More evangelism is nice, but you're still limited by Archangel's CD. The 4pc is just "okay" as well; it lets us use PoH 2 (maybe 3 with tons of haste) times without breaking our mana bar. But people are already using PoH right after Archangel, so not much of a difference.
I guess it would be only compared to a holy pally as they are on our tier.
2pc: 25% chance on light of dawn for a free word of glory
4pc: Word of glory has a 20% chance to give a light of dawn
I know very little of paladins, so I have no idea the strength of those bonuses