I don't really understand
Yes, that's apparent.
Pal is a CHR class. Every point of CHR bonus is +1 AB *for the team* on Mark (and for Seelah herself with Smite). All of her other abilities use CHR as well, CHR to saves etc...
The game has two classes of enemies, bosses and non-bosses. It's worth it to sacrifice some always on stuff to be able to spike the team on bosses because there is such a gap between the two. That's what makes the rnd/lvl and limited use per rest stuff good even if there weren't a lot more rest available. On Unfair I've run into AC (and nat 20) issues with regular mobs, but you should still be able to hit them with solid team play. It's the bosses where that's an issue.
In general physical stat bonuses are much easier to come by than caster stats so I lean that way anyway, but on Pal it's a no-brainer. Once you're there you can look at saves on things that are free action econ, AoE, and/or high # of procs. Stuff like that even 25% chance of beating a save makes an impact and if you're consistently applying Sicken (from Edge), Shaken, and Archon's (mostly from Cleric) you can get it higher than that without much investment. Your relevant stuff in those categories is Evocation (no Challenge Evil) so you're looking at two Feats and a Mythic for +4 DC, which is steep. The sheer number of saves it effects with Archon's it may still be worth it. If I go that way I trade Shatter for it + Improved Initiative since she already spikes the team so well.
I don't really understand the point of these offensive Spells on Paladins. If you're building your Paladin in such a way that he can reliably beat enemy Saves, all you're getting is just a very gimped Cleric.
And if you're building it for melee you're a very gimped Elder Dragon. Irrelevant. She's on the team for Mark and Fear Immunity and several other Pal unique things plus this setting turns on all Pal abilities cancelling the downside of the class. This is
Daidre's subpar fallacy. That's only relevant when deciding what to bring. Once she's there the question is how to get the most out of her.
No reason for the Paladin to waste slots on this, that's the Cleric's/Oracle's job.
... every buff the Paladin/Ranger handles is one more slot for the higher DC Cleric/Wiz to cast something save beating. I thought this was basic.
Daidre has already pointed out how crowded fourth-level slots are for Cleric so this extends your Cleric's number of slots, the more and longer lasting per Pal level. MGW is particularly good because it's hour/lvl so doesn't care about lower Pal CL (saving slots for Wiz Hastes alternatively). Likewise if your Divine Caster is Daeran you can let the Pal handle the situational stuff since it's non-spontaneous.
There is a trade-off between doing that and unique Paladin spells but the unique Pal spells at third level aren't that great for the context (limited number of Good melee companions for Holy Whisper for instance), while Death Ward and Resto are situational things you can switch in and out of.
Shield of Faith gives you the same Deflection bonus, the DR of 10 isn't really impressive at the point in the game when you get the Spell (though putting a Stoneskin on top of it ain't half bad), you don't need a bonus on Saves against poison when there's a way to make yourself immune to it via Communal Delay Poison which is a long-lasting buff. The bonus to all Saves against Evil in an AoE is nice, though.
Yeah, freeing up six Cloak slots (more like four but I don't sweat saves as much on ranged anyway) is kind of good. Especially when there are two of the Skin Flaying Cloaks in game.
Again tho with Shield of Faith it's one slot for six (or however many SoFs you usually keep up). I use those for Divine Favors to turn the Cleric into a full BAB class (with Stunning Barrier for Crusader) but there's a lot you can do with it. DR/Evil is mostly garbage since most Demons bypass it, but there are some foes that don't. The point is Pal gets the spell at lvl 13 where even straight Sorc/Oracle doesn't until 16. 13 is pretty damn early for an Eighth Level Wiz/Cleric spell. Even Wiz Cleric doesn't until 15 and Seelah is in much better position in combat to get the most out of it.
This one is objectively trash, because the earliest you can get it is at level 13, and you'd have to squint real hard to notice a difference from getting an additional 1d6 damage per hit at that point in the game. Good luck trying to Stagger anything with it too.
Luck is the residue of design. That one is pretty late game, but it's save or die on Crit and late game she does get some crits even without Shatter since she's autoconfirming. I've even picked up Shatter on the back-end when I go Evo focus so it ends up proccing a good bit.
Stagger's not save or die but it's a nice one on some of the more dangerous regular mobs with a ton of attacks. Those are easier to hit and have lower saves. On bosses I'm already debuffing saves in various ways so even at 25% chance of beating the save I've got her on high # number of attax mode with Balance Defender (+3 AB on Sword and Shield) so boss has to dodge a lot of them.