I did play a seer during the betas, Got him to 27. I did not have trouble dps wise until I hit the mid 20's. And then the trouble only came from the quests/missions that were supposed to be group quests. I was soloing them and died a few times due to the lower dps. But for the main part , a seer can dps trash and level much easier then most other MMO healers I have ever played.