I'm calling it now; Paladins will fare best, but Shamans will be the hardest hit by the upcoming changes, especially with respect to raiding. I think this change is driven in no small part by Blizzard's realization that Sunwell-level raid guilds are hugely dependent on the party-specific buffs like totems and Heroism/Bloodlust that Shamans bring. The problem is that Shamans are still the least-played class, which has left raiding guilds desperate for a high-end population of Shamans that simply does not exist (especially Alliance-side). Making Shaman totems and Heroism/Bloodlust buff the entire raid (but heavily nerfing how often the raid can benefit from the latter) means the days of stacking Shamans (or trying to) are effectively over.
Paladin changes, especially for holy and retribution, are equally driven by Blizzard's experience with Sunwell. With absolutely breathtaking amounts of raid damage occurring, encounters were disproportionately weighted in favor of: a). healers with more raid-healing capacity, like resto Shamans and CoH Priests (something we heard from SK Gaming months ago) and b). DPS who brought raid-wide DPS buffs to kill the boss as fast as possible (e.g. Retribution Paladins on Brutallus and M'uru). Given the new skills I'm seeing on other healing specs, I'll make another prediction; prepare to see that same level of raid damage rear its ugly head in Naxxramas again.
I'll be launching a more extensive prediction post once talents and skills are finalized for Wrath, and then I'd like to do a follow-up post at some point after guilds start conquering level 80 raid content to see whether they were any good.