Nethaera: Who will be able to use it?
Ghostcrawler: Players who have reached the maximum level will be able to set up dual specs.
Nethaera: Why do players need to be max level in order to do this?
Ghostcrawler: We didn’t want to burden lower-level players with extra complexity as they’re working to level up and learn their class. But if the feature proves popular we might consider expanding it.
Tallying up all of my characters, I have over 800 combined levels. I play every class and I have tried nearly every spec. Dual specs was something I was looking forward to for the sake of my alts, the majority of whom are around level 70.
Please reconsider not making this feature available to characters that haven't hit the level cap yet. Being able to tank or heal instances, yet switch to a spec optimal for soloing, would allow players like me to level with much more variety. I'm not a hardcore leveler in the sense that I only do what's optimal for XP -- sometimes I like to do instances to take a break from questing.
You'd also be helping out players who have DPS mains or alts (mages, warlocks, hunters, and rogues) who struggle to find groups because of the lack of tanks and healers while leveling. I have been playing since the open beta; I was completely new to MMOs, and I learned how to instance by joining groups for things like Ragefire Chasm or Shadowfang Keep. There are very few groups now for certain level ranges (for example, apart from Hellfire Ramparts and Blood Furnace, very few people do TBC dungeons on the servers I play on -- which is a shame because they're a step up from Azeroth dungeons in complexity). One of the key reasons for the dearth of groups is that people don't want to step up to fill in the crucial roles of healer or tank, and not being spec'd for those roles is definitely a contributing factor.
It's better to foster instancing skills (like applying and maintaining CC, or assisting the tank) in low level instances than the level cap, where veteran players will have much higher expectations of the DPS that they invite. I wouldn't consider myself to be elitist, but when forming groups for Heroics, I will turn down DPS that appear to be undergeared or clueless. I'm much more likely to invite someone who's new to the game to a lowbie instance (in a group for Dire Maul, the level 60+ hunter who didn't know what Flare was comes to mind).
Don't underestimate your new players. With a push in the right direction, I'm sure that they can catch on quickly. The WoW interface has become much more complex since the game's inception, but by keeping it intuitive, players have adjusted. Consider the pet and mount interface. Players learned how to use their mounts after they disappeared from their bags; word of mouth, and announcements/tips, were sufficient to keep people from running around on foot for the rest of their tenures in WoW.
The TL;DR version:
1. Dual specs before the level cap will foster more instance groups (and use/enjoyment of old content)
2. More groups will allow newer players to learn how to perform in instances
3. New players can be smarter than you guys give them credit for
In conclusion... Won't somebody think of the alts?! =D