Even if your speculation is correct, it doesn't add anything to the discussion.
Originally Posted by Nephilheim
The 10% mana cost increase isn't that big of a deal really. 700, and 600 mana respectively. As for holy light, it's only 200 more mana. I frequent arena a lot, and when I face mirror comps being (Holy paladin, Feral druid), I heal 30 minute matches with that skullbash debuff on me. It isn't noticeable to the point of breaking us, so I don't believe it will do much in PVE either.
The 5% nerf to walk in the light would be far more substantial than a 10% mana cost on those 3 spells. Holy light spam is still going to be able to be done indefinately; the only thing that this nerf really hurts is how often we can cast DL compared to HL.
I'm fairly certain the 5% nerf went through as a result of the bugged conviction being fixed. We were missing 9% of +healing from that talent for who knows how long. I just wish that they would have reduced the % healing gain from conviction instead of nerf the passive spec bonus.