Blizzard has been overthrowing the status quo before (turning vanilla PvP specs into TBC raid specs and vice versa) and WotLK looks like there will be some upheaval once more.

On top of that, they've been trying to up the viability of pretty much every single spec for PvP (hello MS-Fury!). As a result, it's hard (for me) to see how Arena and other PvP (BGs/World) will shape out to be.

Are there specs that still appear to be favourable each class ? Does it vary per bracket like it does now (with e.g. Holy Paladins largely sitting in 5v5) ?

How well has Blizzard succeeded in making under-represented specs Arena viable ? Take viable as 'able to reach at least the full epic (Hateful) set' to have a bit clearer definition. As an example:
I'll admit, in part, to being motivated by the fact that I'll be leveling some hybrids and am curious about what choice would be the better one for them, but largely I hope to simply get the bigger picture as so far data has been a bit sparse.

[e] Added Hateful.

The way mana regeneration is being handled is a bit tricky at the moment, and will affect all teams (except like, double rogue 2s)

It is now assumed in pve (10 man, 25 man) that you will have a class around who can provide the replenishment buff. Everyone's mana regen is now based around this principle. The likelihood that you will have a survival hunter/ ret paladin / shadow priest on your arena team is obviously low enough, especially in 3v3 and 2v2, that classes really shouldn't be balanced around it.

Meanwhile, everyone's mana usage has increased and the regeneration model has moved away from the player himself, and onto external sources which are very often not available in the arena. It's a problem with no easy solutions.

Long story short: "Mana war" games will end significantly faster.

I don't see how that's a bad thing, myself. And I'm inclined to think that anyone that has ever been in a drain vs. drain match would agree.

It's bad because it unbalances mana vs other resources? (Assuming anyone thinks mana vs rage/energy is balanced now).

Actually, I think it might reduce the imbalance, given the right parameters. Warriors and rogues can't heal themselves (much). When they're on their own, their limited resource pool is their health. The reason rage/energy becomes so powerful is because they can be paired with a healer who will take forever to run out of mana so that when they face off against teams whose DPS also have mana limitations, they can outlast them. If healers' mana usage rates are more comparable to DPS mana usage rates, then this advantage will be less significant.

That's a pretty strict definition of viable, when you consider what a small percentage of the arena population should be able to reach 2200 by design (not counting win-trading, paying for powerleveling and other cheats). The developers still project some specs ending up as more powerful/popular than others in arena.

They're clearly giving classes more pvp tools across a range of trees, but that's only part of the story: synergy with other classes determines your arena potential in the long run. I think the safest projection is that, where now one encounters a diverse 2v2 lineup pool in the 1600s which quickly narrows in the 1800s, one might see that diversity extend maybe to the 1800s and beyond. But there is no reason to expect that the range of lineups won't steadily narrow as the ratings increase, though the actual lineups at top will surely vary with the metagame. It's still rock-paper-scissors, hopefully with a more responsive balancing team this time around.

So you think War/Rogue + Healer will be as mana limited as a Mana User + Healer? Of course it won't. Healers have always had more longevity than DPS, especially with drinking in arenas.

I disagree. There is no need to theorycraft any of this, just log on the PTR or beta and use your normal gameplay, I guarantee that most classes will notice that they are burning through mana at a faster rate. Maybe druids get to have the same (completely balanced) regen as on live, I have not played one so I do not know, but I have played priest/shaman/mage pretty extensively and those classes' personal mana regen is certainly not higher, let alone the same. Is it really an 'improvement' if you are now spending more mana to get the same job done, and personal regeneration has not caught up? Resto shamans are easy to pick on regarding thier basic tools: Spell interruption mana cost went up 500%, casted heal mana costs went up 26%, random stuff like dropping a windfury totem went up 400%. Again, I could be wrong but I am convinced that almost no one will claim that their net mana regeneration is better compared to live.

I said it might be lessened, and in any case you can't be more screwed than totally screwed, which is how it is right now. In this comparison 2v2 teams break down sort of like this:

War/rogue+healer
Double DPS
Drain+healer
Non-drain mana-based DPS+healer

Of these categories, double DPS should be mostly unaffected because they were primarily health-limited to begin with (teams using a DPS spec of a class that can heal may be hurt a little bit, but given that these teams already don't heal if they can avoid it, I doubt it will be a major effect). Drain teams are only helped by a reduction in mana endurance, and the latter category is already largely non-viable. The only category that is clearly hurt is the first. How much they are hurt and whether or not the breakdown is actually damaging to the others remains to be seen.

At this point I'm not concerned about mana regen numbers on PTR/Beta because, as the developers have posted quite a few times already, they're far from done with those numbers and they expect to keep tweaking them after the WOTLK launch. Season 5 won't be starting anytime soon. What I do see is they've added actual tools in the forms of talents and skills that both address mana conservation and work in an arena setting.

I don't know if the mana regen effect on Imp. Leader of the Pack, say, is currently enough-- but its obvious to me that the basic mechanism is capable of correcting the issue, if they tune it right. Good grief, if they're actually trying to fix the feral druid's mana issues in arena, anything is possible.

It's honestly hard to say at this point, given the typical quality of player on beta is not very good. From personal experience, cleave teams are dominating in an absolute fashion.

Blizzard did kill efficiency, yes, but they've also stated that this was on purpose. It's not a particularly bad things for arenas, as nobody (I hope) enjoys fighting 30+ minute to multi-hour games, but it definitely has not seen a 'balancing' pass (DPS hugely outscales healing in Arenas).

Anyway, what you can see at this point:
Holy Paladins are the best healer. Huge throughput and hard to OOM.
Ret/DK are the premiere classes (overpowered), with Mut and Mages behind them.
RNG is at an all-time high, despite Mace Stun being removed.
DPS largely outscales healing.
Efficiency is [mostly] much lower.

It's too early to tell where people will end up speccing for arenas because there isn't much serious competition and things will likely change still. Will there be specific specs for most classes best for arenas? Yes. You just might have a second viable spec you can use for a different type of comp/bracket.

Are you really seeing Holy paladins dominating healing over druid/priest teams in beta, especially after the Infusion change (no instant holy lights)? Output has gone up a fair amount, but the vulnerability to lockouts and poor mobility hasn't changed much, so that is surprising if true.

I think Beacon of Light will go a long way in helping Paladins avoid being locked out and controlled. A paladin can now use Beacon of Light to heal an ally without ever stepping into LOS by just healing yourself, it also increases your thouroughput by tons whenever your fighting a team that switches often or that dots up multiple people on your team. This is of course assuming your actually picking up beacon of light in your spec as I think 37/0/34 is going to be viable because of the current state of JoW.

It doesn't work that way. You have to actually be wounded for the heals on you to matter with beacon. Also, JoTW was changed so that it is useless for a holy spec because it returns base mana instead of actual mana.

Exactly what do you mean by "cleave" teams?

Full physical dps.

Lots of variation but the classic 'cleave' comps are:
In 3v3 Warrior enhSham rDruid
In 5v5 hPaladin dPriest War enhSham Rogue

But yeah, any team with full physical damage.

Looking at the numbers for mana burn, it went up 50% in effectiveness (1000->1500), while mana pools have about doubled (10k->20k). But while in that respect it is certainly less imposing, I don't see how it has been nerfed into "uselessness." If you are allowed to cast for a few seconds you can still flip any close mana match on its head.

The only odd thing is that Viper sting roughly doubled in effect (1400-3000) while drain mana only went up about 20% (200-240/tick), so they have apparently intentionally chosen not to scale all drain effects the same.

Thoughts on the best professions for WotLK Arenas?

e.g. for healers, melee dps, ranged dps?

Also, with the racial changes, thoughts on good, acceptable and bad Horde race choices for each class?

e.g.:
Class: Good / Acceptable / Bad - comment

Example:
Horde Priest: Undead / Troll, Blood Elf - WotF unparalleled as an extra CC break

Gnomes are quite strong for rogues, especially Mutilate that has no access to improved sprint. The Engineering boot-enchant as well as the rocket launchers also look very good. As a second profession I think Leatherworking looks best.

With it's high mana cost to us, it is very often not worth using because our opponent has a way to regain the mana that we have drained (innervate, divine plea, tide - which is obviously the weakest of the 3), while we still do not have the same ability to replenish the mana required to cast mana burn. Drinking is an obvious way to regain mana - but all other healers have the potential to set up situations to drink as well. However unlike the other healers, if we get away from out opponents to drink for a few moments, we will only be regain mana from drinking - whereas druids/shaman/paladins can take this time to safely innervate/tide/divine plea without worry of dispel.

My stab at Horde side:
Priest, Mage, Warlock, Rogue
- Undead still. Will as a CC break is too good to pass up.
- Troll and Blood Elf get out classed by WotF. Troll Priests lose their Mini-MS.

Shaman, Hunter, Warrior
- Not sure. I lean Orc, because of Blood Fury (which lost its self-MS) and Stun duration
- For Hunter, Orc has the 5% pet damage in its favor, especially for BM 4dps builds.
- Tauren has War Stomp and the new and nerfed 5% base health.
- Troll has snare duration reduction and berserking.
- For warrior, not sure how good UD is now that Berserker Rage is usable in any stance; seems like overkill

Death Knight
- Not sure. I haven't played with DK PvP builds at 80, so I don't know often Lichborne gets specced into. I'd imagine often, however. It does have its disadvantages, though, as it turns you into Undead -- i.e. you can get shackled and turn eviled. Clicking off Lichborne, last I checked, didn't remove the shackle.
- Undead has Will in its favor, a valuable CC break
- Orc has 5% pet damage in its favor. Perhaps pet damage will matter? Not sure. Also stun resist and Blood Fury.
- Tauren has War Stomp and the new and nerfed 5% base health.
- Blood Elf has 2% resist magic; Troll has snare duration reduction and berserking. I think both are outclassed by the other three.