I think in Blizzard's mind (not arguing whether or not it makes sense), the increased healing done by raid cooldowns getting higher 10 to 25 man target caps does not count as throughput when it comes to class balance. Their reason for putting those target cap increases there in the first place was to compensate for damage reduction cooldowns effectively being 2.5 times as effective in 25 mans while healing cooldowns don't scale. Arguably, they probably also don't even count the amount healed by the cooldowns themselves, because Devo Aura and PW: Barrier do not show up as throughput but the healing based raid cooldowns do.
Here is what average HPS for T15 looks like for 25H (all parses).
Holy Priest 98736
Disc Priest 91054 (-8%)
Resto Druid 87322 (-13%)
Mistweaver 87243 (-13%)
Holy Paladin 86799 (-14%)
Resto Shaman 78962 (-25%)
Now, if you were to follow my theory and remove the typical healing done by Divine Hymn, Tranquility, Revival and Healing Tide Totem (pulled numbers from our logs of 25H farm clears) from the output numbers, this is what the numbers look like.
Disc Priest 91054
Holy Paladin 86799 (-5%)
Holy Priest 86295 (-6%)
Resto Druid 76843 (-18%)
Mistweaver 76076 (-20%)
Resto Shaman 70750 (-29%)
Those are the numbers Blizzard is probably balancing around given their rationale for the 25 man target caps on raid cooldowns, and it probably explains why they think Paladins will be fine. Of course, you can argue that Devo Aura and PW: Barrier are not as good as the other cooldowns at the 10 man level and make an argument to have them buffed.