Either let Rogues and Mages have a Tank or Heal spec that is on par with other Hybrid classes… OR freaking make them the absolute best there is at what they do, which is kill shit!And although as a druid he obviously doesn't say "nerf druids", in the end that is what this results in: If a specialized class is "freaking the absolute best at what they do", hybrid classes can't be the best at that, and thus end up being second-best at everything. Whether you arrive at that point by nerfing one class, or by boosting all the others, doesn't really matter. But Blizzard appears to go down the "nerf druids" way, by what I read from the PTR. Even leading druids agree that their class shouldn't be the best at everything!
Basically before dual spec hybrids had a good argument why they should be as good as specialized classes, by saying that their advantage of being flexible was only a theoretical one. A healing druid was likely to remain a tree for every raid, and the fact that his class could either tank very well or dps quite good didn't give him any real advantage in that raid. After dual spec that advantage stops being theoretical. Sure, the druid still needs to collect a second set or armor and glyphs. But if a raid leader has to decide between giving a raid spot to a rogue, who even after dual spec can only deal damage in different ways, or to a druid, who can be a reserve healer or tank at the same time, why would he choose the rogue? He'd only choose the rogue if the rogue deals somewhat better damage than the druid.
In other words, the introduction of dual spec helps hybrids much more than more specialized classes, thus class balance must be reviewed taking that into account, and making specialized classes better at what they do than hybrid classes. Rogues should deal more damage than dps warriors, who should deal more damage than cat druids. Warriors should tank as well (if differently) as death knights, but better than paladins or druids. Priest should heal and deal damage as well as shamans, but better than paladins or druids. Not a lot more, but enough to compensate for the added flexibility of druids and paladins.
Now Spinks is going to accuse me of blaming dual spec for unrelated WoW problems. But he is in error when he thinks that dual spec and class balance isn't related. I'm not against dual spec, although I don't see me having a dps spec on my priest yet, I don't really like shadow. But it isn't as if the introduction of dual spec is class balance neutral. It helps some classes more than other classes, and that has to be taken into account.
What Forever a Noob sees as a disadvantage, that people will use different specs depending on how many tanks and healers a given encounter needs, I see as an advantage. I'm pretty sure that you can negotiate with your raid leader or fellow healers / tanks who is going to switch to dps, and who remains in his previous role. With my priest I might end up doing dual-spec for discipline and holy, and have an convincing argument why it is better for me to switch between two different healing roles instead of switching to a dps role. Not *every* healer and tank in a raid will need to be able to switch to dps, and some people will probably enjoy the switch.