I think the cost increase to 500g is bad for the server. This will mean a loss in quantity and quality of healers and tanks for dungeons.
The overall leveling experience will suffer from this, and might lead to frustrating newcomers.
Why even a cost to it.. Let players have a dungeon and a leveling spec from the start.
Dual Specialization didn't even exist in Burning Crusade.
Players had plenty of "quantity and quality of healers and tanks," their leveling experience didn't "suffer" for not having something that didn't exist, nor were they (or anyone going to a private server play the expansion) "led to frustration" over it.