For Retribution:

Buffs:
Attack Power: Very easy to pick up with plenty of free talent points.
Damage %: Next patch it will be 40 yards, which should help buff ranged players (those that have to be elsewere obviously lose out on it). Free talent points means its no issue to get.
Haste %: Next patch it will be 40 yards, which should help buff ranged players (those that have to be elsewere obviously lose out on it). Also again, plenty of free talent points to spend here.
Replenishment: Replenishment will be up easily with no issues other a minor detail with the possibility of resist if under capped (not likely next patch).

Debuffs:
Crit Chance: no issue ever. The only way for it to fall off for a brief moment would require two resists on judgement (unlikely).
Judgements: Much easier time keeping these up than a holy paladin.

Overall, I see no dps costs for keeping any of these benefits up.

It is currently painful for hunters to maintain Scorpid debuff (hit reduction for boss).
The reason is that most builds requires the serpent sting.

MM definitely will be hurt a lot, because of Chimera Shot.
BM uses it, because of the sustained shot glyph, giving +10% of damage to sustained shot (their main attack) if the serpent dot is on the target. So, using scorpid instead is, let's say, around 3% dps loss (that's a pure guess, taking yellow damage as one third of total damage. More data are needed).
For the current build, SV uses it, for the Lock and Load procs. They can do without it, but that's a loss again, because of the procs you don't gain, and because of the glyph for sustained shots.

It may be best for hunters to apply the debuff. But answer is not so clear for me, so more numbers are needed.
One advantage of hunters is that they can apply it for the "critical" part of the fights, and use serpent other time if they want.

Bleed Damage Increase
* Cat Druid: 30% Swipe damage or 9% FB damage from spec change, ~125 single target DPS
* Bear Druid: Required Threat Ability
* Arms Warrior: 2 talent points = 5 rage off execute or Blood Frenzy if already applied by a Rogue (likely with 3.1 changes) or various utility

5% Melee Crit
* Cat Druid: No other talents to potentially increase DPS earlier in tree, required to get further.
* Bear Druid: Required to get to Mangle
* Fury Warrior: 1 talent point = 3 rage off execute

frmorrison: I had missed the 3.1 selfishness of UR for Enh Shamans, good call. But damnit, now I have to recruit another one. I also fail to see how doubling the effect of Retribution Aura (or whatever aura he's using) with Aura Mastery doesn't qualify as a worthwhile raid Buff. Certainly Divine Sacrifice and Divine Guardian provide excellent utility, but my current assumption is that Protection Paladins are the best source of this buff given the additional desire for Blessing of Sanctuary. Perhaps taking a Prot Paladin is not worth gaining reliable 3% damage reduction on everyone, but I'm not about to start a "who makes the best tank" debate.

theothersteve, and others: The Attack Speed slow inevitably comes down to if there's a Frost DPS DK in raid or not, the opportunity cost of any other DPS class applying it is too high, though I am being lead to understand that Frost DPS is not going to be viable anymore. The end result is that every tank spec should have the ability to apply the debuff except in cases like S+3 with 3 tank where a DK or Warrior "off tanking" is going to be the better source of the debuff than a druid or paladin (this was the basis of my decision, which was wrong), the majority of the time, when you need more than 1 tank, they are not going to be able to provide debuffs for each other reliably. My main point was that my current view of maximizing buffs insists on having Paladins and Warriors to tank for their unique buffs (technically Sunder isn't unique, but I doubt any other tank makes it worth -Armor (major) coming from a DPS class).

Ttyl: Looking at top WMO's on Patchwerk, Serpent Sting is 3%-4% Hunter DPS, IS is 4%-6% Moonkin DPS, so a 30% increase to IS is the lesser of the 2. Moonkin glyph should look for another Glyph I guess (Glyph of Focus is likely a higher DPS glyph anyway when the extra range isn't needed)

Frost mages won't have a DPS loss strictly due to maintaining the debuff (or Replinishment) since it is applied with our No. 1 spell (Frostbolt). The only time we would not be doing something that maintains both the debuff and replinishment is if we are using a Fireball from a Brain Freeze, Ice Lancing on a Fingers of Frost (keeps the debuff running, but not replinshment) or when we have to be highly mobile due to some fight mechanic.

Also, after 3.1, you will have to take into consideration that Fire or Frost mages will apply 5%.

Edit: corrected a stupid mistake I made.

Aura Mastery only doubles the base effect of the Aura for a few seconds every two minutes. In the case of Retribution Aura, enemies would take 200 holy damage for attacking a PC instead of 100. Not exactly earthshaking. It's not going to be a core talent for any spec of paladin.

Winter's Chill and Improved Scorch do not stack, before or after 3.1.

Yea, Enhancement are going to be spec'ing UR regardless of anything else, since we'll get 9 Expertise from doing so. Nobody will pass that up. It makes 10% atk power a non-issue, really. Marks Hunters, Blood DKs and Enhance Shaman automatically pick up their version of the this buff - the first because it's 1 talent point and the latters because of personal benefit.

20% melee haste is a little more of an issue - If you have a Frost DK, I believe they usually pick up the talent. It requires they Icy Touch, though, and has talent prereqs, but they gain 5% haste from the talent itself. Enhancement puts 2 points into Imp. Windfury for 4% haste and no benefit. Frost DK would be the better choice, imo, given the option.

Moonkin:

E&M: 13% Spell damage is free (single target), but may not be up until 10s into fight depending on opening sequence.

IFF: Minor armor debuff and 3% spell hit. In 3.1 is 1 GCD every 5 minutes (per target). In 3.09 it is every 40s (3% DPS loss).

Moonkin Form: 3% Haste and 5% crit. Passive.

Insect Swarm: 3% miss debuff. Usually 'kin Glyph out of this for extra DPS. Losing the glyph is about a 1% to 1.5% DPS loss. Usually uptime for IS is around 70%. Requiring 100% uptime would hurt DPS by a little (I'd guess 0.5% to 1.5%).

The talent provides 3% crit on targets affected with ANY faerie fire, so probably no.

So long as the raid contains a properly specced Spriest, there's no reason for a Moonkin to cast Faerie Fire (in fact, it becomes detrimental if you're also using a Feral Tank). Taking the iFF talent is a DPS boost (but is likely one of the first dropped to gain mana regen), casting it is what causes the DPS loss.

Correct me if I'm wrong, but there was a thread in the tanking forums a while back confirming that Feral Faerie Fire can be applied to a mob regardless of the presence of Misery or IFF debuffs, assuming the detriment you're referring to is a Bear tank being unable to access FFF's threat.

Major is from worms which are exotic pets, so BM only. They lose quite a lot of dps from it as it is not a ferocity pet, didn't check the exact numbers.
Minor is from wasps which can be used by every hunter, loss of about 150 dps when used instead of a wolf according to the spreadsheet.