|Arrow of Death - At 8th level, an arcane archer can create an arrow of death that forces the target, if damaged by the arrow’s attack, to make a DC 15 + 1/2 Arcane Archer level + 1/2 BAB Fortitude save or be slain immediately. It takes one day to make an arrow of death, and the arrow only functions for the arcane archer who created it. The arrow of death lasts no longer than one year, and the archer can only have one such arrow in existence at a time. An Arrow of Death may still be split by the Split Arrows class feature, or any similar effect.|
|Arrow of Death: Save DC based on half of your BAB? Dude, that's crazy. 10 + class level + spellcasting mod is what I'd recommend.|
With the build as is, minimum level you're going to get Arrow of Death is character level 15 (this account for Level 1 casting class, and 6 levels of a full BAB progression class
Death Arrow save is going to be 15+7+7 = DC 29
Comparable save or die from a level 15 caster, assuming a base casting stat of 24 and a level 7 spell:
10 + 7 + 7 = DC 24
This does not include ways to increase caster level and spell difficulty. And the Arcane archer can only do this one, and then takes at least an hour to get it back... assuming he stops everything right there and starts to craft another arrow.
Now, if you take level 20 arcane arher, same as above. If you assume a BAB of +18 and a caster level of +18 (which I'm sure is possible somewhere out there in build land), and a caster stat again of +24. You can have:
1. One death arrow, DC 15 + 10 + 9 = DC 34 Save or die
2. Imbue a level 8 save or die spell, DC 10 + 8 + 7 = DC 25 Save or die. Shoot 4 arrows, how it split into 8 arrows, now you have 8 save-or-die arrows.
I'd prefer #2, personally.
I would suggest you just make Death arrow a 1/hr ability, and ignore the whole crafting idea.