One of the most difficult things for me in regards to switching from Holy to Disc, is learning how to bubble properly. Since I rarely use Power Word: Shield when I run Holy, and since I'm a habit-based healer, I knew that training myself to bubble properly would be tricky.
I originally suspected that I would not bubble enough, so when I started as Disc, I forced myself to bubble all the time. As I mentioned before, this actually turned out to be a bad thing - I bubbled too often when people wouldn't take damage, and therefore spent far too much mana on bubbles without benefiting from Rapture. In effect, it's no different than overhealing. I was bubbling often enough to try and keep weakened soul up on every member of my five man at first, before I began to realize that was over-doing it.
I ran several heroics this past weekend, and my primary intent was to learn to bubble properly. Here are some of the tips I picked up for bubbling in a 5 man:
It's usually a good idea to keep a bubble up on yourself, whether or not you know you will be taking damage, but I don't think you need to worry about bubbling often enough to maintain Weakened Soul.
If there is not a lot of group wide damage, and all the damage can effectively be picked up by the tank, then do not waste your mana bubbling the rest of the DPS.
Squishy, high threat DPS (i.e. mages) who may have occasional trouble with aggro, particularly when there are multiple mobs and they are providing AoE damage, are good candidates for full time Bubblage. However, again, I do not find it necessary to bubble enough to maintain constant Weakened Soul.
When there is group wide damage, it is then a good idea to bubble all members of your party. If everyone is likely to take a fairly large amount of unavoidable damage, this may warrant maintaining weakened soul on everyone, as best as you can.
Regardless of the circumstances, be sure to bubble people often enough to keep up Renewed Hope buff for the whole party.
Bubbling properly is one of the trickiest arts to master as a new Disc Priest, so I will likely be posting more information about various Bubbling tips and suggestions as I gain more experience.
I know there are several Disc Priests who read this blog, so please provide more suggestions about proper bubbling procedures for the five man scenario in the comments - I'd love to hear them! I'll post about bubbling in raids at a later date.
Eventually I intend to put all of this information together into one long guide specifically on the art of bubbles for new Disc Priests. It's become something of an obsession with me, because as a healer, mana usage and mana regen is always on my mind - and for Disc Priests, bubble management is fundamental for mana management. I hear all the time about how Disc Priests should not have problems with mana, so I am trying to get to a point where I feel I can say that about myself as well.