Both specs could use fine tuning compared to the other classes, most classes seem to be pulling ahead due to the 'random' damage that can be easily healed through smart heals, which priests lack except for CoH and Cascade. When damage is both predictable and effects entire groups priests become stronger. For an example, Massive Attacks in the Spirit Kings encounter or Titan Gas in Will of the Emperor.
In terms of mana management, I struggle to oom playing disc. I spend a fair bit of time casting solace when I can easily get away with it when its not a significant HPS loss.
Priests aren't significantly behind. They have roles that they are strong at and some they're weak at currently. Just wait till your in full BiS and can snipe every heal