Dual specs are a fix for a problem that is already addressed. I would be fine if they would use this feature to allow people use PvE and PvP no matter which class and spec they play. This was the main issue with specs from the beginning. It wasn't so much a PvE problem. I think dual specs will lead to lazy class design for PvE. Right now Blizzard has to make every spec kinda viable for PvE and PvP. What I see happening is certain specs getting shorhorned into pure PvE/PvP viability.
From a PvE standpoint I see only downsides for spec switching. Again this opens up a door for min-maxing, something I thought was a thing of the past. Think about people building the best specs for certain bosses. Such thinks will happen and such things aren't what this feature is trying to address.
Duel specs is not going to make DPS spec'd players into healers or tanks. Duels specs will allow healers/tanks to run dps, pvp, farm, solo quest and so on. The reason for this is simple. Tanking and healing both are different games then DPS.
A good healer can't spam heals, they need to really choose their heals only when needed. A good tank is even more crutial. It took me about 4 levels to really get the hang of things when my Paldin switched from Ret/holy to protection. To be a great tank you need to know your tank skills, when to use them, when not to use them, you need a good set of tanking gear(uncritable, avoiding/blocking almost every hit). Some people will do fine with duel specs, but I'm telling you overnight tanks and healers won't spring out of nowhere.
Dual specs won't necessarily be in patch 3.1. Apparently patch 3.1 isn't expected before March 2009, and even if it had dual spec included, it would be too late to help me leveling my characters. My Priest just hit level 76 yesterday, and by March I'll certainly have both the Priest and Warrior at level 80. Maybe not the Mage and the Death Knight, but I don't see the Mage gaining a lot of utility from the dual spec feature anyway. I guess most of the people who are against the dual spec feature are playing one of the classes it doesn't help much. Most Warriors and Priests I know would be delighted when it was introduced. Well, it might still help at level 80 for soloing daily quests etc., but I'd much rather have had it already for leveling up. Unfortunately leveling in WotLK is too fast. And with "too fast" I mean you spend just one month to get to level 80, and then nearly 2 years at level 80, unless you play a lot of alts.
So Dual specs might be nice, but I'll still end out respeccing the old fashioned way to fill the third slot, heck depending on how they implement things, dual specs might actually make that more of a pain rather than less.
At least if Blizzard takes more time to implement this feature, there is a good chance that they get it right. Everyone has a different idea of how the dual spec feature should look.
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