So, were we on the mark with our guesses?
Absolutely! We were on the mark with both the good aspects of the spec's anticipated performance and the not so great factors as well.
Disclaimer: much of this discussion is really only valid at this point of the game as we only have 61 talent points to muck about with, however, many of the points discussed about now will be entirely valid at level 80 as well.
So, what were the spec specifics? Well, the spec that was tested did not have Meditation, which severely limited my effective duration in combat. We expect this to be marginally resolved with WotLK with the extra talent points, however, we do have concerns as to gear itemization as mentioned in a previous article . We tried to fill in as many of the crit talents as possible, minimized the spirit talents and stacked crit over spirit, primarily through wearing Shadow PvE gear. Additionally, we skipped many of the AoE healing talents, but did take Circle of Healing, mainly because it is instant cast. Gear wise, we didn't expect to survive much longer than usual, with our ~200 resilience, but our spec supported it in that it wasn't tailored for longevity.
The 'shine' of the spec came with countering burst damage and when healing unmolested, big Flash Heals and Greater Heals came through to keep people alive. With a higher crit rate than a typical healing Priest, Surge of Light and Holy Concentration procs came at a respectable rate, granting free Flash Heals and hasted Greater Heals. I greatly recommend getting some kind of proc notification mod to inform you of either proc as they can greatly assist overcoming burst situations or staying out of the 5 second rule. The key thing to remember here is that while the emphasis, talent wise, is on casted heals, the typical instant mitigation abilities available to all Priests (Power Word: Shield, Prayer of Mending, Renew) are almost as strong as those of a Discipline spec. Therefore, the instants are still the 'go to' abilities before chaining casted heals.
While the improved casted heals are able to help mitigate burst, Guardian Spirit (calls upon a guardian spirit to watch over the friendly target. The spirit increases the healing received by the target by 40%, and also prevents the target from dying by sacrificing itself. This sacrifice terminates the effect but heals the target of 50% of their maximum health. Lasts 10 sec) turned out to be an amazingly strong talent, possibly better than Pain Suppression. In a Battleground world, focus fire from several opponents can essentially burn a target down very quickly. In such cases, Pain Suppression may not be enough to mitigate the incoming damage, and often, targets die with under the effects of Pain Suppression. This is where Guardian Spirit shines. While it is on its target, not only does it increase healing done to the target by 40%, but it also acts like a Cheat Death effect if the target dies, and let's be honest here.. how many people hate when their kill target gets saved by Cheat Death? Just as I thought... everybody.
(Note: If the opposing faction comes a rollin' into your city to kill your faction leader, try to time a Guardian Spirit right before they die. It can bring about some wonderful results.)
As an example of the talent synergy, last night, with Guardian Spirit on my target, I cast a 5400+ crit Flash Heal which proc'd Surge of Light and Holy Concentration. This, in turn, gave me 2 hasted Greater Heals and a free/instant Flash Heal. It's these types of crazy proc combinations that keep people alive to turn the tide. Unfortunately, a Bladestorming Warrior and a Ret Paladin proceeded to destroy me for stealing their kill... only to have my broken form turn into a Spirit of Redemption and continue to keep everyone topped off.
My Warlock buddy and I joked that with my undergeared status, my healing in Spirit of Redemption probably outweighed my regular healing and as funny as it might be, it may have seemed to be true. With 200 resilience and less than 9k unbuffed health, Blessed Resilience and Blessed Recovery really didn't help that much. Saving myself in this burst environment was all up to whether or not I prep'd myself with Shield/Mending/Renew and had my trinket up and had Psychic Scream off cooldown and possibly had Guardian Spirit off cooldown, as well.
So, would I recommend this spec? Absolutely. Especially if you're undergeared, give this spec a try. I don't think anyone without max resilience (and a couple of pocket healers) expects to tank multiple DPS in BG's these days, so giving yourself a few options that maximize your 'up' time is probably the best option at this point.
There are a few downsides to this spec and they are the aforementioned mana longevity issue, a much slower Mass Dispel and a reliance on random crits to possibly counter burst. In addition to all of that, there are very few 'tricks' that a Deep Holy Priest has up his sleeves. The lack of Power Infusion, Borrowed Time, and Improved Mana Burn turn Deep Holy into a dedicated healbot, which may or may not fit your playstyle.