With more cards, almost all lists become harder to narrow down. There are many options for a deck like this and I'm pretty sure I can't cover all of them, so I won't even try. :D

However, I will try to address a few of the tech/preference choices I see.

• Confessor Paletress vs. Ysera: At the end of my climb, I wanted to try out the Confessor. Mainly because I got her from a pack and was curious. :) However, I also realized that a lot of the games centered around the hero power in the lategame. In an aggressive matchup, dropping Ysera became pretty hard, because you always want to heal something/yourself.  In a control matchup, most opponents have answers to Ysera. For both scenarios, I thought that getting two bodies and a heal (sometimes for four, because of the Justicar) would be more worthwile. I just played three games with this version, for two of them, the change was completely irrelevant, so I'm still not sure about these two cards. However, if you want to see the merits of the Confessor over Ysera, you can watch the very last game of the video linked above. :D I talk about my thoughts of the Confessor here as well.
• Only 1x Shadow Word: Death: With two Lightbombs and Vol'jin, another SW:D doesn't seem necessary. However, since there are a lot of targets for SW:D out there, it might not even be bad to run two ... it's hard to find a card to cut for it though.
• No Holy Champion: I am somewhat excited to try this card, especially since it fills a gap in the 4-slot. Again, it's hard to think about cards to cut for it.
• Justicar Trueheart: I wasn't really sold on this card, when it was revealed first. However, it can pull a lot of weight in this deck. Healing yourself for four every turn can bring you out of Hunter range where you would usually stay in the same range for several turns. Where this might be a better niche for Antique Healbot, it still fills a lot of different purposes, too. You can heal an Injured Blademaster to full health and you can deal a lot of damage with Auchenai Soulpriest, making your hero power 4x as good as a Mage's hero power! The body is also aggressive enough to force a response (which, granted, isn't too hard to come up with most of the time).
• 1x Light of the Naaru: I thought about adding Flash Heal instead, but found that the body attached to the spell usually soaked up more damage, especially since it always threatens to grow out of control if it stays unanswered.
• No Thoughtsteal: The only matchup I really missed it was against Control Warrior and maybe against Handlock. So if you see a lot of them, adding at least one Thoughtsteal seems reasonable.

There are a lot of other cards to think about. However, since the deck worked fine for me, I didn't feel the need to do further adjustments. At least for now. :)

The deck has multiple win conditions, depending on both matchup and draws. Sometimes you win by presenting and keeping a board alive that can't be dealt with, sometimes you win via card advantage through drawing a bunch of cards, sometimes you win via card advantage by clearing your opponent's board and sometimes you win simply by outlasting. Priest decks are situational by tradition, so I will shortly address the core combos.

• Northshire Cleric + Holy Nova/Circle of Healing: Can deal with your opponent's board, heal your board and draw you cards! Ching, ching!
• Wild Pyromancer+Spells, especially Power Word: Shield: Dealing damage to all minions can both help you to draw cards (see above) or to simply deal with a lot of minions that some decks (Paladins, Zoo, ...) tend to throw on the board. :)
• Injured Blademaster+Circle of Healing/Light of the Naaru: Getting a 4/7 out on turn 3 (or on turn 2 with coin) can make you feel you're playing Druid. The body is hard to deal with for most classes and can also be healed up in combination with Northshire cleric.
• Auchenai Soulpriest+Circle of Healing: Flamestrike for 4 mana. If you have spare mana, you can also hit something for two/four more damage with hero power, for three more with Light of the Naaru, etc.
• Zombie Chow+Auchenai Soulpriest: I was surprised by the amount of games where I could apply some serious pressure simply by dropping an Auchenai turn 4 to sacrifice my Zombie Chow for an additional 5 damage. In some matchups, most noticeably Handlock, having both Auchenai and Zombie Chow(s) in the lategame can make for some serious pushes, especially combined with the improved hero power. 2x Zombie Chow,
• Justicar at 10 mana: Sometimes, you want to remember yourself that you can use your hero power, play the Justicar and use your hero power again at ten mana. :)

Interestingly enough, the mulligans don't really change with the matchup. Usually, you want to try to establish an early board presence, forcing your opponent to respond. However, if you don't get the draws for it, you might simply have to stall until you can come back with Auchenai+Circle, Holy Nova, Lightbomb, Belcher, etc.

• Circle of Healing: Can draw you cards with Northshire Cleric, can pump up an Injured Blademaster, can help keeping your minions alive and can potentially clear your opponent's board with Auchenai Soulpriest. Good keep. :)
• Zombie Chow, Northshire Cleric, Wild Pyromancer: Having something to play early is important in almost every matchups. Dropping turn 1 Cleric is pretty much always correct if you don't expect your opponent to have an answer that is better than a 1-for-1 (Fiery War Axe) or if you have a Shield to play on it the turn afterwards.
• As metioned, keeping Power Word: Shield with early minions is suitable, but bad if you don't have anything to cast it on already.
• Dark Cultist / Injured Blademaster: Dark Cultist is an annoying minion to deal with early and you always hope to find a circle for your Blademaster. You usually don't want to keep both Cultists going first. Dropping Blademaster without anything else is okay in a pressuring matchup where you need to buy some time.
• Harrison Jones: Definitely a keep against Warriors and Rogues. If you have other minions to play early, obviously a nice keep against Hunters and Paladins, too. Remember to keep your coin if you want to counter a Truesilver Champion or Death's Bite.
• Vol'jin / Shadow Word: Death: If you are certain (like, definitely certain!) that your opponent plays Handlock, keeping these two cards can help you getting some momentum against his turn 4/5 threats.

• Druid: Druids don't run board clears, so spamming minions and keeping them alive is almost always a good idea. Starting off with Blademaster+Circle gives a lot of early momentum Druids usually can't handle too well. However, their ramping abilities are sometimes hard to counter. Since people started adding Ancient of Wars again, it's sometimes better to clear bigger minions (like Dr. Boom) with Lightbombs, so that you can kill an AoW with SW:D to gain tempo. Lightbomb also helps a lot to get rid of stealthed Shades to mitigate combo damage. Feels about even.
• Warrior: Games against Warriors can end quickly or go into fatigue, especially since it's hard to figure out, what time of Warrior you're up against. If you figure out that it's Control Warrior and that you didn't have a pressuring start, you can switch to one of two approaches: One aims on drawing a lot of cards to out-value your opponent, the other one aims on barely drawing cards since the game will go into fatigue. It pretty much depends on the hand size of your opponent which strategy might be suitable, but this is definitely a matchup that can easily go into fatigue, where the Justicar is a big help.
  Against Patrons, you want to force them to move their removal and resources early so they have not enough cards for big combos. If you fail, there will probably be a big Frothing Berserker turn that kills if, even with 30 health.
• Hunter: Getting early board presense with one of the smaller bodies helps a lot. Since Hunters usually don't run any card draw (maybe King's Elekk), you can usually out-value them. Simply try to clear their stuff and to stay alive as much as possible, then they will run out of steam while you can fill your board up. :)
• Mage: There are still a lot of Mage archetypes out there and I'm glad I didn't face any Freeze Mages. Mech and Tempo Mages should be a favorable matchup since you can usually fight their board quite well and stay also stay alive. It's a little bit harder than against Hunters if they run Arcane Intellect though, since it will take longer to outlast them.
• Paladin: Uther is all over the place at the moment, but the decklists differ a lot. The only real threat in the Secret Paladin matchup is the Mysterious Challenger though. After it came down, your first attack will almost always trigger Noble Sacrifice which will trigger Avenge and Redemption. If you have a Lightbomb, SW:D or Vol'jin, you should trigger these secrets first (and, in case of SW:D, try to let the Avenge hit the Challenger), so you can easily clear his stuff. The other two untriggered secrets will then be Competitive Spirit and Repentance. Letting the first going off with one or two minions is usually not a big deal, the latter should be played around as good as possible.
• Priest: The mirror match is always a little weird. Getting a healthy Injured Blademaster on the board is usually a big deal as well as drawing a bunch of cards in the early game. Priest minions are usually pretty bad in killing each other (more health than attack), so getting something out that can actually kill something or getting a lot of stuff injured and healing them all up with a Cleric on the board are both viable strategies early. The games will unfold pretty differently, depending on what specific list your opponent runs.
• Rogue: I didn't spot many of them, but I feel that having two Lightbombs in the deck helps to deny them a board where they can simply one-shot you with Oils. Getting Harrison to put a buffed weapon in the museum or to draw two cards from a full dagger to deny them tempo can help a lot.
• Shaman: If you don't face some weird OTK Shaman, Auchenai+Circle helps a lot in clearing a big board that they will definitely try to set up as soon as possible. Cabal almost always hits a target and the Shaman's healing totem can be abused to draw cards with Cleric if suitable. If you can, set up an early board presence to deny them their flood and to make them waste their resources. Your lategame becomes a lot better if they feel forced to use Hex on some early or midgame minions.
• Warlock: Against Zoo, the playstyle don't differ too much from matchups against Mages, Hunters or Paladins. Against Handlock though, you require a pretty specific set of answers against their threats. I usually don't play around too much stuff and try to pressure as hard as possible. Having Vol'jin for a turn 4 threat, SW:D for an early giant and Lightbombs to clear bigger stuff latter helps a lot. Pressure can also be applied through Zombie Chows + Auchenai and through Justicar's improved hero power and Auchenai. It's still a rough matchup and when Lord Jaraxxus comes down, you can either kill him during the next two turns or you'll probably lose.