You can’t rest the first four levels if you want to get everything before Defense triggers. You can’t rest in Garrison without losing Haste. If you’re not abusing reloads then blowing your wad on map locations risks getting ambushed on World Map until your Stealth is high enough to avoid.
Leper’s Smile and Lost Chapel require some rest management as does Drezen now that Corruption was turned back on. If you’re running an Arcane buffer *and* a DC caster that’s two slots that significantly cut into what else you can do. For Divine, Abundant(x2) is a lot stronger when you want to get Crusader’s Edge on team and/or use strong Divine self-buffs for fighting. Likewise getting Dispel, Greater up ASAP. Nenio Illusion control is great but also takes Abundant to apply to non-boss fights in midlevels.
And then there’s Barkskins, Alch sharing Personal, unique Bard spells, Pal Veils/Fear Immunity AoE/early Angelic, Greater, etc… It isn’t straightforward, especially with Lann, Wend, Reg, Ulb, and Greybor all non-casters.
You can rest an infinite amount of time in the maze, it doesn't matter. Outside of the maze, you will get a couple of rests before the tavern defense actually triggers and you don't need to do much combat in order to not miss anything: hit the tower of Estrod, resolve the conflict between Hulrun and Ramien and save the crusaders in the library (which can be done without fighting). Obviously get Ember and Woljif. You don't need to clear every single location on the map before tavern defense.
Early game offensive spellcasting is purely Grease + Glitterdust and you don't need to spam these spells: one spell per encounter where they are needed is enough when used by a proper DC caster.
Leper's Smile and Lost Chapel are far enough into the game that you will not have any problems with spell management as long as you're actually playing a properly built and properly supported DC caster (Evil Eye, Insightful Contemplation, Touch of Law support).
Using an arcane DC caster and an arcane buffer in the same party is not suboptimal, because a Witch can be an arcane buffer while also providing hex spam (Evil Eye, Protective Luck) that benefits the entire party. Witch + Shaman evil eyes stack and can be used to debuff boss saves, making them vulnerable to disables or instant death, so there's a reason to bring BOTH a Witch (arcane buffer) and a Shaman (divine/arcane buffer) in the same party along with a Cleric (domain user). Here's a one-round unfair vescavor queen kill to demonstrate the party synergy:
Note how it rolls precisely 11 on the save, because it's forced to roll precisely 11 via Touch of Law.
Abundant casting is absolutely worthless for divine casters for several reasons. First, Shamans don't need it, because they should get Enduring Spells ASAP instead as all of their spells should only be used for buffing (they have no Insightful Contemplation synergy due to being WIS-based and thus will always have pathetic spell DC). Secondly, Clerics don't need it either, because they should be focused on getting all the good domains (Law, Madness, Community, Good) as well as Domain Zealot online ASAP, then get Enduring Spells to make their buffs actually last. When using spells strictly for buffs, both Shaman and Cleric will have more than enough spellslots without Abundant Casting.
Crusader's Edge is completely irrelevant garbage on a divine caster due to garbage spell DC. It should only be used on a dedicated arcane transmuter with high transmutation spell DC, obtaining the spell requires Loremaster level(s).
Dispel is needed only on a single dedicated dispeller who should be your arcane DC caster, because arcane casters get bonus feats and can take the dispel-supporting feats (Dispel Focus, Greater Dispel Focus, Dispel Synergy, Destructive Dispel and possibly even Spell Specialization: Greater Dispel) without gimping their entire build due to such heavy feat investment. Moreover, making your DC caster a dedicated dispeller has extra synergy: Dispel Synergy debuffs saves only for the dispeller so the DC caster can actually benefit from it and Destructive Dispel DC scales with your main casting stat which is buffed via Insightful Contemplation in the case of a INT/CHA caster.
Yes, I know Oracles exist and technically can be made into offensive casters, but they are worthless garbage, because they have neither hexes, nor cleric domains and will always be at a spell DC disadvantage relative to arcane casters due to lack of unique class spell DC boosting abilities like Potent Magic, School Power, Foretell-Hinder, Aura of Despair, Fey Bloodline Arcana and Overwhelming Spell. Using them as pure buffers is a waste of a party slot, because Clerics/Shamans can buff AND provide domains/hexes.
Abundant spells are worthless on Nenio, because when properly built she will be reliably disabling even the hardest unfair encounters with one spell and you already get more than enough spells in chapter 3:
As a DC caster, Nenio should be using her Mythic Feats to stack 5 Expanded Arsenals for 5 different schools and her Mythic Abilities to get school-specific synergy (e.g. best Jokes for Enchantment, Corruptor for Conjuration) and Favorite Metamagics.
