[Snarky Soujo]

I'll address some labbed builds here in a moment, I think the passive is fundamentally flawed for Reapers rather than Appy's.

Reaper gains little to no benefit outside of dark bard builds with Tuning Fork. With Tuning fork, Dark Bard Priest becomes a menace of a build, with its drawback being some stat stretching however;

You gain:
95-105 crit evade
Dark Bard Parry + normal-average defenses
Elemental resists with song
Elemental attack ranging 10+ with the stage effect
280 hit depending on hit increasing accessories + purity edge

Reapers suck in this regard because spellcasting with spears, you would always, ALWAYS want to be using the respective elemental staves as they are BIS for casting.
+5 ele attack and perfect scaling stats for their respective elements.

If Reapers get some extra stats, I'd expect this build to be more proficient than it already would be.

Addressing Axes;

With Appys, it would be limited in what effect it has.

With Strength builds, fire comes to mind as a main build, and you are almost certainly wanting to use their respective spelledge weapon, transforming weapon (axe tome), or using a material like fossil.

Ice has a fairly good material too for aquarian spellcasting, albeit better for ice, rather than water.
Wind, I'd be questioning what brought you here.
Nature/lightning, the material is fairly bad but doable.

I don't think the sanctity passive should be kept as it is, I'd be interested to see the swa/stat efficiency of sanc investment vs arcanic or material changes. My intuition says its usually better for the latter.

If it were up to me I'd change it entirely to be encapsulated in Macabre culture as follows:

Macabre Culture: You gain 2 elemental attack respective to their remains for every piece of gear you are wearing. If all pieces of your gear are the same material you can cast the domain of magic whilst wielding a spear/axe.

I'd be interested to see what builds could come out of that, feels more focused to the race and it's lore.