I thought it was hunter / x
Cuz hunters aren't exactly survivability gods, and their tactics to win an arena are quite simple, despite not being exactly easily countered: CC healer, kill DPS. However, hunters already have some serious countercomps in 2s in the form of hybrid - healer comps.
If you look at the current top hunter double dps comps in 2s, those would be: hunter/ret and hunter/feral. Now, look at the classes involved and how these comps fair:
- hunter ret has hunters getting nerfed, plus is already is heavily counter-comped by a fair amount of things, such as shadowpriest/healer, priest/feral, priest/mage.
- hunter feral has hunters getting nerfed and ferals getting dogged on, especially on the utility part which is what makes them good in this comp. Let alone that any comp with a fear will already make their lives miserable.
Now, would any hunter double dps comp arise? Nothing you can point to, since BM will not be as effective with the loss of silencing shot, and not actually having triple trinket in the first 30 seconds definitely makes hunters a much worst choice for a double dps then they currently are.
On the other hand, check the current version of warlock/moonkin, and ask a few questions:
1) what are they currently hard countered by?
2) what incoming nerfs/buffs are they receiving?
3) what would potentially hard counter them in the next patch - i.e. classes receiving major buffs?
The answers to these questions would be:
1) rogue + another melee most likely, because of the heavy lock down pressure in the openers. However, rogue + melee is not a regular setup in 2s. Apart from that, sure moonkin warlock can lose to a variety of healer/dps, but they aren't hard countered by any of those, which means they can also win the games if they outplay the opponents.
2) there is a mix of nerfs and buffs coming warlock's way, such as gateway cooldown increased to 1m and KJ cunning being nerfed a bit. On the other hand, they are receiving baseline howl of terror. How will these affect the setup? To be fair, not very much. Noone needs a "get out of jail free" card every 15 seconds. Once per minute, on top of the other regular defenses, is really enough. The KJ cunning nerf in a double dps won't be gamebreaking in helping opponents to stop fears, especially since it's offset by baseline howl. The moonkins are losing NS, which is a significant loss, but moonkin healing doesn't rely that much on it, especially in lock/moonkin setup.
3) Apart from the obvious double dps rogue based, once again thanks to too great initial pressure, there wouldn't be a setup that could potentially hard counter warlock moonkin. Furthermore, hybrid / healer comps look significantly worst then now (i.e. feral/disc). This all leaves room for moonkin/warlock to outplay their opponents.
So all in all, moonkin/warlock is now and will be in my opinion the single best double dps setup you can play.