Hello, I'm Typing Hazard.
I've been playing Pixel Dungeon since something like 2012? 2013? I stopped when weapon durability hit, and only picked up Shattered about 2 years ago. I ascend just about every day, never play challenges because I don't like them and why would I ever do things I dislike? I like Sniper, I like Monk, I like Freerunner. The other subclasses are fine too actually. I don't really have a 'main'. I run 'em all. It's nice.
I've been playing nothing but Cleric since the beta (save the one Huntress run I did after the Shared Upgrades bonus was changed, but oops it was bugged and it was extremely broken lol) and have tried to really weigh the pros and cons of the subclasses against both what Cleric's main themes appear to be, and how this game treats other characters with similar roles.
Here's my TLDR -- Paladin has a high level of cohesion, a very directed and synergistic set of abilities and a powerful rework of the tier 1 abilities that define the subclass. Meanwhile, Priest has a series of tier 3 abilities that do not directly empower the others, don't really provide a meaningful tier 1 rework, and really just feels like a disparate bag of tricks that provide some fringe benefits to the stated goals of the class that don't quite land.
I'll drill down on these in a minute but I feel it's a good time to post the standard disclaimer about how this really is just the opinion of a regular player. I'm open to disagreements here, I'm usually pretty glad to be wrong about the power level assessment of a given subclass in the game (when I first picked up Sniper I thought it was a pile, but it turns out I just had much to learn).
Even before Paladin came out, my strongest Priest runs were never wand-based. They were nearly all melee runs; the tome didn't have increased recharge yet, and running out of charges meant you were literally a completely unskilled character without a single passive skill to assist you in combat, so with charge management being constantly front-of-mind I habitually played Priest like the tome was just a big "in case of emergency, break glass" box and fell back on strong armor and melee weapons to get by.
When Paladin hit, that strategy was rewarded in spades. The tier 1 abilities come surging back; Holy Weapon powers up Paladin's Smite, which in turn boosts its duration (all skills do this of course), and Aura of Protection works directly with Holy Ward to grant a ton of damage reduction. These all stack with your existing glyphs and enchantments, empowering Paladin to be a real force in melee range.
Returning to Priest after seeing how effective and deeply synergistic Paladin is, left me feeling like Priest goes wide with its strategies - maybe a little too wide. Holy Lance is potent, but very... balanced for fairness. 4 charges and 50 turns is a lot of spam prevention and given what happens to a Priest when their charges are spent, I'm not sure the 50 turns is warranted as you'll pay through the nose if you let yourself spend all your charges on a couple of Lances.
Hallowed Ground is awkwardly stronger for melee focused characters than ranged; it permits an opportunity to put space between you and the mobs, but it also messes up line-of-sight by letting grass pop up everywhere and it confers shielding as long as you stay in the consecrated area, so its full bonus requires you to maintain a certain distance from the target(s) you're trying to get space from. The shielding and grass work very well for a melee character as gaining shields while giving you multiple ways of surprise attacking can be quite powerful, but when you're trying to maximize your distance while being able to see what you're actually shooting at, it gets awkward. We have a workaround in Divine Sense but now we're talking about spending 4 charges on this strategy, and spending 4 charges to not just one-shot something with Holy Lance warrants a lot of thinking, because spending 4 charges is very costly.
Mnemonic Prayer is one of those tough-to-evaluate skills as it can extend some of the more fundamental mechanics in the game. I get the sense that there are lots of yet-to-be-discovered interactions with it that go beyond just boosting buffs on yourself or extending the duration of various debuffs on enemies. More to the point though - it's not Cleanse. Cleanse is a house of an ability. It might be the strongest tier 3 ability in the game; wiping away status ailments and gaining 30 health is very strong. It compares directly to Meditate, as it encompasses several of its functions, and apparently trades recharging for instant speed, which feels like an amazing trade. Both Priest and Paladin have utility skills that rarely feel worth taking over Cleanse, which makes it significant over most of the rest of the tier 3 "generic" class abilities - I don't often find myself prioritizing the shared tier 3 abilities of classes unless I have some super-strong undeniable reason to grab one over a subclass ability. With Cleanse though, I feel I have to have a really compelling reason not to take it, and even then it probably still gets at least the one leftover skill point you have left after drinking a Potion of Divine Inspiration and maxing 3 other tier 3 skills.
More than just the tier 3 skills of Priest though, the Tier 1 rework isn't giving much power to Priest. Guiding Light itself doesn't deal much damage, but it's not meant to, it's meant to Illuminate a target which in turn confers bonus damage to wand/artifact/ally usage and guarantees a melee hit. The actual benefit of this bonus damage is a little hard to quantify without getting spreadsheet-y; is a single hit of flat damage equal to Priest's level worth the incredibly low damage turn of using Guiding Light? A lot of the time it's as fast or faster to use your offensive wand twice in a row, and the number of turns you spend until you've dealt lethal damage is important since that's time the enemy has to close in on you. In a way it compares unfavorably to something like Wand of Magic Missile, which is a modest damage source on its own but also grants extra levels to the wands in your inventory - so they get more damage and bigger effects.
Another unfortunate issue with the Priest's tier 1 rework is that it doesn't really apply to as many skills as Paladin's. When Paladin buffs Holy Weapon and Holy Ward, I have a tome full of spells that will do work for me throughout the entire dungeon. When I open it I don't really have any "dead" spells, I haven't over-leveled to the point where the tier 1 spells just aren't applicable anymore. It works a lot like the other active ability menus for other characters; Gladiator and Monk gain all their active abilities at once and they all have their use cases. Priest's rework enhances Guiding Light and the passive Illuminate status, but Holy Weapon and Holy Ward just fall off. They're still in the tome, but rarely if ever will they come back into play. They're largely forgettable, which is a shame as Guiding Light itself doesn't really have that much use in the later stages of the dungeon or during ascent.
My Priest runs where I've tried to lean into the long-range aspect of the class have left me feeling like the support just isn't there. Holy Lance is strong but expensive and infrequent, Hallowed Ground is half-help and half-hurt, Mnemonic Prayer is not Cleanse.
I hate to end with a series of suggestions, because I'm not a game dev, so I won't do that. I know that there is some kind of data collection involving who succeeds with which characters and what gear and so on, and knowing that is probably more informative of what skills "need" altering, if any - after all this isn't a series of objective observations, just my experience and feeling after running nothing but Cleric since the beta hit. So I can't propose a solution and it would sound trite if I did anyway; but I am definitely interested in a dialog with some other players here about how they feel about Priest and Paladin, and how their relative power levels measure up to each other, and what if anything they would agree or disagree with.