Arrow was forgettable in P:K but with Rod you've got a chunk of 60 Divine damage (vs Touch AC) with a Daze attached vs Demons. Very solid 2nd level spell. Can up damage with meta if you want to go that way.
Searing Touch is no save. Medium Range instead of Close. Good vs Undead like Zach who have no SR. Holy Smite/Order's Wrath turns Arrow of Law into AoE with Blind/Daze depending on which one you use. Also Medium range so easier to avoid own team, or just send Seelah in since she's immune to both.
Boneshatter goes up to 90 with no attack roll needed and adds exhaustion/fatigue. Also attacks Fort instead of Will.
Flame Strike takes it AoE and a 50 pt Breath has a lot better chance to revive something than if you need a roll. It says friendly but people have said can be used against Undead/Playful?
Recovery is Medium Range and ends up healing/damaging more pts. Plague Storm (bypasses SR!) gets a lot more serious if it's -8 DEX AoE or -4 STR with Blind. Daeran/Ember has Beneficial Curse that can boost Disease DC by two while making them immune.
Maxxing Summons is always good but look at what Max Rod does to Undeath to Death! Ghosts must die.
And then there's the obvious. Note that Cold Ice Strike is Swift. Daeran with Second Mystery Waves can tack a Slow onto Cold spells.