Uh, I don't really feel shortchanged. I mean, we're not getting nearly as awesome stuff as tanks/retribution, but Holy is still getting some really neat stuff.
I do agree with Ike's statement that Ret won't be the abandoned raid class anymore though, although not necessarily that Holy would be the dumped class if one has to be dumped.
You don't generally say no to a healer or tank while forming a raid unless you happened to have too many available or they're undergeared. It's not like they're exactly -that- plentiful compared to DPS. Still, I imagine that the ridicule/stigma for playing a retadin will go waaaaaaaaaaaaay down.
As for your aura question....your description of threat isn't -quite- accurate/complete.
Technically speaking, a prot pally generates the majority of their threat through holy damage due to Righteous Fury. You do generate it from other sources too, but primarily, holy damage is what gives you threat.
Retribution Aura does holy damage as mobs hit you, and if you've already grabbed multiple mobs, you have an easier time of holding them all because each time they hit you, you generate threat by doing some holy damage on them through that aura, meaning there's less chance they'll peel off and start attacking healers or dps because of their own aggro generation.
Ergo, when tanking multiple mobs, retribution aura can often be the best choice. Obviously, that's not always true, since sometimes a mob hits like a truck and you want to have your fire/shadow/frost resistance or devotion aura for whatever help they can provide. And you can (and will) still generate AoE threat through concecrate anyhow.
While devotion is getting a nice upgrade, that just means you'll be using it more often, not that you'll necessarily be using it all the time. Auras are pretty situational to what you're fighting, honestly, even now.
