Looking at this topic made me realize, all of my clerics have (slightly) different spell lineups. I have four clerics (65, 71, 80, 85) and their lineups seem to vary widely but are largely due to the tanks and support they're typically paired with and the content they're usually working with. (spell type/role in bold)
65
Complete Heal
Holy Light
Holy Elixir
Mark of Retribution
Word of Replenishment (group heal)
Supernal Remedy
Ethereal Elixir (group heal over time)
Word of Redemption (group CH)
Divine Barrier
Since she still melees a lot and doesn't have the AA count of my higher clerics, she keeps DB up for aggro management (sometimes a good string of procs can steal aggro from my monk or littlest rogue, at least for a couple rounds). Because her gear level is so far beyond the content she does (up to EP but mostly in Valor/BoT), I load her up with all her various heal tricks. Sometimes I'll swap out the group CH for a nuke (rarely) or stun (usually) since it's rare to have more than one person in the group taking major damage. And if they do, that's what the DivArb/Celestial regen combo are for.
71
Pious Elixir
Complete Heal
Desperate Renewal (long recast heal & cure)
Ancient Hallowed Light
Sacred Remedy
Elixir of Divinity (group HoT)
Word of Vivification (group heal)
(swap slot, usually Mark of the Righteous)
Mark (currently 'of Kings')
With her AA count (1135 atm), CH is just a placeholder for Promised at 73. I only use CH when I'm semi-afk really, since the tanks she's mainly paired with (72 warrior, 71 paladin) take care of their own health pretty well (paladin) or don't need much in the way of heals. Plus, with the crit rate she has, I've gone hours XPing using Lights (with a few elixirs) with the typical abundant healing and healing boon procs/crits.
80
Solemn Remedy
Solemn Light
Solemn Elixir
Promised Restoration
Chromassault (chromatic nuke)
Sound of Resonance (non-pushback stun)
Word of Vivacity (group heal)
Swap slot (was Eleventh-hour but now it's Blood of the Devoted)
Divine Destiny (DA)
She's probably my most developed cleric overall. With 1850 AA, I can count on crits so I don't really need as many tools as I actively use. That gives me a lot more choice in how I approach each scenario.
My 85 is inactive atm so can't check her lineup. But I don't mem Gate regularly because I don't need it (99.6% of the time, there's a druid or wizard in group) and I don't mem root for similar reasons (there's always someone else in the group with that tool or a better one like snare, mez, charm, etc). It should be noted that I don't do pickup groups (though I do pickup stragglers on occasion) and I know my tanks and groupmates very well (intimately in most cases, since they're me as well). Pre-75, I usually don't even bother memming nukes since IMO, even after being tweaked, cleric nukes are largely a wasted spell slot. I typically put Vow (cleric uber melee buff) up and then replace it in the swap slot with something else. If they're meleeing, I keep Ward memmed. I'm also not typically a stickler for efficiency since I usually have far more mana than I need.
As far as what spells I think a good cleric should/must have, that's easy. You should have the highest Aego upgrade and symbol you have access to. You should also have the highest light, remedy, elixir, group heal, and group elixir you have access to. All of these should be RK2 or better, post-70. Dunno if the Temperance mention was just a lingo issue or intended but at 70, Temp is useless IMO (unless you've found a way to advance your cleric by buffing low levels). I say 'lingo issue' because it might not be known that Aegolism was the first cleric combo buff (Temp is a downgraded, low level version of it as Virtue, Conviction, Tenacity, Temerity, and Gallantry are upgraded versions), despite the level indications.
But I look at it like this: as long as you can keep your group up in level appropriate content, you're fine. Depending on server, it can be hard for returnees to build up the resources to keep their spellbooks filled and up to date (even with vendor sold RK1s). Just be sure to remember not to stress yourself trying to keep the overaggroing caster upright. It's often more efficient to rez them (especially with 1.0 or Blessing of Resurrection) than blow your mana healing them (and thus spreading downtime throughout the group). (Note: this is coming from someone who plays 3 wizards, 2 mages, and 2 necros as well as a 'zerker, 3 rogues, and 2 rangers. I learned very early on (in the South Karana days, in fact) to throttle back my damage output if the tank is having issues with aggro).
All that said, welcome back! Get ready for fabled season. You might find a multitude of upgrades and in my experience, folks are always glad to add healers (and DPS).
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Rendition
Cazic Thule
Maxim
Firiona Vie
Collusion
Test